Restoring line chat history from iCloud backup

Then you need to contact that app's developers if there is a flaw or bug or incorrect instructions with their app. Do they not have a help or support web site with some method of direct contact? Since this is not an Apple app, you need to deal with Line about this.

I just finished dealing with this problem. Hopefully you will see this if you haven't already solved it yourself.

1. On your iPhone 6, go to Settings > Account, and be sure to fill out the Phone number and email address fields and also log in with Facebook.

2. On your iPhone 6, go to Settings > Chats & calls > Chat history backup > Back up now. (You've already done this step)

3. On your iPhone 7, *REINSTALL* Line. Then go to Sign In and log in with Facebook (important). It will warn you that Line data (chat history) on your iPhone 6 will be deleted because Line can only be used on one account at a time. This will not delete your Line account.

4. A prompt to backup your chat history from iCloud should appear once you successfully login.

Please let me know if this has helped anybody.

Chats got restored but Audio messages and pictures vanished. Backed up 486mb when in total there was over 1.2 Gb

See if this helps - https://help.line.me/line/ios/?contentId=20000428

I have synced a new iPhone to iTune then Line chats have been restored from iCloud to iPhone.