You still need to transfer your LINE account after restoring from an iTunes or iCloud backup. To do so, follow the steps below.
1. Open LINE on the main device your account is registered to.
2. Tap Verify on the "Please verify your identity" screen.
3. Enter your registered email address and password, then tap OK.
Note: If you forgot your password, see [When transferring your LINE account] If you forgot your password.
4. If the "How to finish transferring your account" screen appears, turn ON Skip 2-step authentication on your previous device, then tap Continue on your new device.
5. If you see the Update notice screen, tap Verify phone number or Continue with Apple.
If you have any issues transferring your account or can’t use your previous device, see the following Help articles.
The "How to finish transferring your account" screen appeared
[iOS] I can’t use LINE after restoring from an iTunes or iCloud backup