Just my 2c... This method if backup/restore sucks... not because of the OP, but because LINE doesn't have a batch backup/restore option!!! Have hundreds of conversations that I'd like to maintain... which means, hundreds of times of clicking backup etc etc, the hundreds of times clicking restore etc etc.
FYI, if you are willing to root your phone and pay for TIBackup Pro you can simplify the process. Backup LINE (user apps) and your SETTINGS (system apps) with TIBackup. Copy TIBackup folder to external sdcard or PC. Do whatever you were going to do that required you to backup/restore LINE. Load up TIBackup, load up the TIBackup folder, restore LINE APP+DATA, then goto the menu in TIBackup and scroll to the bottom and select 'manage android id' and select restore from backup (if you backed up the correct settings data under system data there will only be ONE option). Your phone will automatically reboot. Click on LINE, boom everything just like it was before.
Does this method also keep group chats as well?
I've backed up my chats one by one but stupid group chats don't offer the "save all" option, only the e-mail text one. I'll probably give this a try anyway...
@TASL, dude, you are the MAN!! Restoring the device ID with TiBu totally worked!! I had no idea this was the problem with this silly LINE app. Thank you!