After arriving in Japan and activating your eSIM, many people may find themselves in situations like, "The signal is not coming in," or "4G or 5G is displayed, but I can't use the internet."
The causes of connectivity issues with Japan's eSIM are often not due to a malfunction of the eSIM itself, but rather related to network selection, data roaming, APN, and network settings.
In this article, we will clearly explain the settings you should check after arriving in Japan, in order of priority. We will also introduce methods for checking settings specific to iPhone and Android, as well as solutions if you still cannot connect after making the settings.
Main Causes of Japan eSIM Connectivity Issues
If your Japan eSIM is not connecting, the following causes are primarily considered.
- The Japan eSIM line is turned OFF
- The Japan eSIM is not selected for mobile data communication
- Data roaming is turned OFF
- APN settings are incorrect
- Network selection is incorrect
- Airplane mode is ON
- The device has not been restarted
- There is an issue with the start date or expiration date
- Out of service area or temporarily weak signal
- The device is not compatible with eSIM
- The SIM lock is not removed
First, please check the settings in order from the top without deleting the eSIM.
You can check the Japan eSIM products and usage conditions at Japan eSIM Products and Pricing Plans.
Settings to Check First After Arrival
1. Turn ON the Japan eSIM Line
Even if you installed the eSIM before departure, it does not guarantee that the line will automatically turn ON after arriving in Japan.
Open the settings screen and check if the line for the purchased Japan eSIM is enabled.
On iPhone, turn ON the option "Turn on this line," and on Android, turn ON "Use SIM."
2. Select Japan eSIM for Mobile Data Communication
Even if the Japan eSIM line is ON, if your usual main line is selected for data communication, you will not be able to connect to the internet via the Japan eSIM.
Please select the Japan eSIM as the line to use for mobile data communication.
3. Turn ON Data Roaming for Japan eSIM
Many travel eSIMs require data roaming to be ON in order to connect to partner networks within Japan.
By turning ON data roaming for the Japan eSIM and keeping the main line OFF, you can more easily prevent unintended international communication charges.
4. Turn OFF Airplane Mode
If airplane mode remains ON after you disembark from the plane, you will not be able to use mobile communication.
Turn OFF airplane mode and wait for about 1 to 3 minutes before checking the connection status.
How to Check Settings on iPhone if Japan eSIM is Not Connecting
On iPhone, check the settings in the following order. The names of the displayed items may vary depending on the iOS version.
Enable the Japan eSIM Line
- Open "Settings"
- Select "Cellular"
- Select the purchased Japan eSIM
- Turn ON "Turn on this line"
Change Mobile Data Communication to Japan eSIM
- Open "Settings"
- Select "Cellular"
- Select "Mobile Data"
- Select the purchased Japan eSIM
If "Allow switching mobile data" is ON, the device may switch to the main line when the signal for the Japan eSIM is weak. If you want to prevent unnecessary international communication, please turn it OFF.
Turn ON Data Roaming
- Open "Settings"
- Select "Cellular"
- Select the Japan eSIM
- Turn ON "Data Roaming"
Check Network Selection
- Open "Settings"
- Select "Cellular"
- Select the Japan eSIM
- Open "Network Selection"
- Turn ON "Automatic"
If you are instructed to select a specific carrier from the purchase source, please turn OFF automatic and select the specified network.
How to Check Settings on Android if Japan eSIM is Not Connecting
On Android, the names of the settings screens may vary by manufacturer and OS. Generally, check in the following order.
Enable the Japan eSIM
- Open "Settings"
- Select "Network & Internet" or "Connections"
- Select "SIM" or "SIM Manager"
- Turn ON the purchased Japan eSIM
Select Japan eSIM for Mobile Data Communication
- Open "Settings"
- Select "SIM" or "SIM Manager"
- Select "Mobile Data"
- Select the Japan eSIM
Turn ON Data Roaming
- Open the settings screen for the Japan eSIM
- Turn ON "Roaming" or "Data Roaming"
Set Network Selection to Automatic
Open "Mobile Network" or "Network Operator" for the Japan eSIM and turn ON automatic selection.
If you cannot find the setting items, please search for "Roaming," "SIM," "APN," etc., in the search bar of the settings screen.
If you are unsure whether your device is compatible with eSIM, please check the list of eSIM compatible devices.
Reasons Why You Can See Signal but Cannot Use the Internet
Even if your device shows a signal or "4G," "LTE," or "5G," you may still be unable to access websites or apps.
In this case, it is possible that you are connected to the mobile network, but there is an issue with the data communication settings.
Incorrect Mobile Data Line
Even if the signal is displayed, if a different line is selected for mobile data communication, you will not be able to communicate with the Japan eSIM.
Data Roaming is OFF
With travel eSIMs, even if you are receiving a signal, you may not be able to connect to the internet if data roaming is OFF.
APN is Not Set Correctly
APN is the connection information needed for your smartphone to connect to the internet.
Most Japan eSIMs are set automatically, but some Android devices and eSIM products may require manual configuration.
If the instructions after purchase include APN, username, password, etc., please enter that information accurately.
Data Allowance is Exhausted
With limited data plans, communication may stop or speed may significantly decrease once the available data allowance is exhausted.
For estimated data usage during your trip, please refer to data usage estimates.
How to Check APN Settings
For iPhone
On iPhone, APN is usually set automatically. If you are able to communicate, there is no need to change the APN.
If you are instructed to set it manually, generally check in the following order.
"Settings" → "Cellular" → "Japan eSIM" → "Cellular Data Network"
If "Cellular Data Network" is not displayed, it is possible that the APN is set automatically or that it is set to a configuration that cannot be changed manually.
For Android
On Android, generally check in the following order.
"Settings" → "Network & Internet" → "SIM" → "Japan eSIM" → "Access Point Names"
On Samsung Galaxy, it may display as "Settings" → "Connections" → "Mobile Networks" → "APN."
If you create a new APN, please save it after entering and select the created APN.
If you are communicating normally, do not change the APN on your own judgment.
Try Airplane Mode and Restarting
Even if there seems to be no problem with the settings, the device may not be correctly recognizing the Japanese network.
Toggle Airplane Mode ON and OFF
- Turn ON Airplane Mode
- Wait for about 10 to 30 seconds
- Turn OFF Airplane Mode
- Wait for about 1 to 3 minutes and check the connection
This operation will cause the device to rescan for communication networks.
Restart the Smartphone
After adding the eSIM, changing the APN, or selecting the network, restarting the device may reflect the settings.
After restarting, temporarily turn OFF Wi-Fi and check if you can open websites using only mobile data communication.
Check Network Selection
Typically, set the network selection to "Automatic."
If you cannot connect with automatic selection, manually selecting the carrier listed in the instructions after purchase may improve the situation.
When selecting manually, do not switch between displayed carriers multiple times; select one and wait a few minutes.
Choosing a network that is not specified in the product may result in being unable to communicate even if the signal is displayed.
Check Start Date and Expiration Date
Even if the settings are correct, you will not be able to communicate if you do not meet the conditions for starting use.
The timing for starting to use the Japan eSIM mainly includes the following types.
- When you first connect to a compatible network in Japan
- The start date specified at the time of purchase
- When the eSIM is installed on the device
- When a certain period has passed since purchase or issuance
Please check the start date, end date, and time zone of the purchased plan.
If you want to choose a plan that matches your stay duration, please also refer to comparison of Japan eSIM pricing and plans.
Move to a Different Location to Check Signal Strength
In places like basements, tunnels, mountainous areas, deep inside buildings, and certain areas of airports, the signal may temporarily weaken.
Please move to the following locations and check the connection status.
- Near a window
- Outside the building
- In the airport arrival lobby
- From underground to above ground
- In a less crowded area
In crowded stations, event venues, and tourist spots, communication speed may temporarily decrease.
Check the Settings of the Main Line
If you are using both the Japan eSIM and your usual SIM, you also need to pay attention to the settings of the main line.
Generally, set it as follows.
- Mobile data communication: Japan eSIM
- Data roaming for Japan eSIM: ON
- Data roaming for the main line: OFF
- Automatic switching of mobile data communication: OFF
If data roaming for the main line is ON, you may incur international communication charges depending on your contract.
If you want to maintain your phone number and SMS, you can keep the main line ON and turn OFF only the data roaming.
For plans with phone numbers, please check eSIM with phone number.
Is it Okay to Delete and Reinstall the Japan eSIM?
Even if the Japan eSIM is not connecting, please do not delete it immediately based on your own judgment.
The QR code for travel eSIMs may only be scannable once. If you delete it from your device, you may not be able to reinstall it using the same QR code.
If you cannot connect, please first perform the following operations.
- Turn the line OFF and then ON again
- Toggle airplane mode ON and OFF
- Restart the device
- Check data roaming
- Check APN and network selection
- Contact support from the purchase source
The conditions for reinstalling after deleting the eSIM vary by product, so it is important not to delete it before receiving guidance from support.
Information to Prepare Before Contacting Support
If you have checked the settings and still cannot connect, please contact support from the purchase source.
Preparing the following information will make it easier to identify the cause.
- Order number
- Start date
- Current location
- Smartphone model name
- OS version
- Displayed carrier name
- Presence of signal or 4G/5G display
- Displayed error messages
- Screenshot of mobile communication settings screen
- Screenshot of APN settings screen
For information on how to contact and what information is needed, please refer to eSIM setup and support information.
Frequently Asked Questions About Japan eSIM Connectivity Issues
Is it a malfunction if it doesn't connect immediately after arriving in Japan?
It is not necessarily a malfunction. After setting the Japan eSIM line, mobile data communication, and data roaming, it may take a few minutes to connect to the network.
What should I do if the signal is not displayed?
Please check the Japan eSIM line, airplane mode, network selection, coverage area, and start date.
You can also try restarting the device and moving outside or near a window to check the connection.
Why can't I connect even though 4G or 5G is displayed?
Please check the mobile data communication line, data roaming, APN settings, and remaining data allowance.
Why can't I connect if I turn OFF Wi-Fi?
Your smartphone is likely in a state where it is only connected via Wi-Fi. Please check if the Japan eSIM is selected for mobile data communication.
Do I need to turn OFF the main line?
It is not necessarily required to turn it OFF. If you want to maintain your usual phone number and SMS, keep the main line ON and turn OFF only the data roaming for the main line.
Is it necessary to set the APN?
For most Japan eSIMs, the APN is set automatically, so manual configuration is not required. Only set it according to the instructions if APN information is provided after purchase.
Will deleting the eSIM fix the issue?
Deleting it does not guarantee a fix. In fact, you may not be able to reinstall it using the same QR code, so please do not delete it before receiving guidance from support.
For other questions, please check frequently asked questions about eSIM.
Conclusion | Check Settings in Order After Arriving in Japan
If your Japan eSIM is not connecting, it is often due to settings related to line selection or data roaming rather than an issue with the eSIM itself.
After arriving, please check in the following order.
- Turn ON the Japan eSIM line
- Select Japan eSIM for mobile data communication
- Turn ON data roaming for Japan eSIM
- Toggle airplane mode ON and OFF
- Restart the smartphone
- Check APN settings
- Check network selection
- Check start date and expiration date
If you have checked the settings and still cannot connect, do not delete the eSIM; please check troubleshooting for when eSIM is not connecting.
If you want to review everything from purchasing to setting up and using the Japan eSIM, please also refer to the complete guide to Japan eSIM.
For those preparing an eSIM for travel to Japan, you can check plans that match your stay duration and data allowance at Japan eSIM Products and Pricing Plans.
