Line account - login isn’t working, 400 bad request

Hi there. Sorry to hear you're having trouble accessing your FC Mobile account. Have you tried logging in using a different device or a different network (Wi-Fi or mobile data) to see if the issue persists?
Could you also try fully restarting your device and setting a different web browser as the default browser on your device?

Let us know the results, and we'll be happy to help further.

Hello, I tried to do everything you told me such as restarting my device or try with mobile data but the issue persists.

However, I tried on another device, an Android phone, and it works. It’s a good news but it’s an old and laggy phone where i dont even have 20 fps. I would prefer playing on my main device.

Thank you for your reply

The fact that you're able to log in successfully on another Android device suggests that your FC Mobile account and LINE credentials are still valid, and the issue may be related to the login authorisation process on your main device.

Could you please try the following:

• Make sure both FC Mobile and the LINE app are fully updated to the latest version.
• Clear the cache for FC Mobile and the LINE app ( if you have it), then restart the device.
• check that Chrome (or your default browser) is updated, and also clear its cache 
• Temporarily disable any VPN, private DNS, ad blocker, or security app that could interfere with the login authorisation.

I disabled my ADblocker and checked that i don’t have any vpn, i cleared the cache… but still nothing works. And in case you need the UID of the account I’m trying to access, it’s: (removed)

Could you also try clearing the app data storage for FC Mobile (not just the cache), then restarting the device and trying again? Check also date and time settings on your device. 

If the issue persists, please let us know your device model, Android version and newtwork. 

My main device is not an Android but an iPhone 13, iOS 26.5.

So since I’m on iOS, I can’t really « clear the app data » but I tried uninstalling and reinstalling FC Mobile but it still doesn’t work. And for the date and time settings they are correct.

So anything new?

May I also confirm which web browser is currently set as your default on your iPhone? Have you tried different options as mentioned above? 
Go to Settings > Apps > Default Apps (or scroll to the specific browser app’s settings), tap Browser App, and select your preferred browser 
Do you also have the Line app on your phone to test it? 

My default browser is Safari but I tried to change it for Google Chrome, and yes I have the Line on my iPhone

Okay. Thanks. Could you also please try the following steps:

1. Sign out of the LINE app completely, then sign back in before opening FC Mobile.
2. Force close both the LINE app and FC Mobile from the app switcher, then try logging in again.
3. Go to Settings -  General -  iPhone Storage  LINE, tap Offload App, then reinstall the LINE app and test again.
4. Make sure your iPhone has at least 2 GB of free storage available.
5. If you're comfortable doing so (and you've confirmed you can sign back into your LINE account), temporarily uninstall the LINE app and then try logging into FC Mobile again.