I recently changed handsets to a Samsung Galaxy S4 and started to restore my Whatsapp message but the restore was interrupted and has not continued the backup. How do I complete the Whatsapp backup restore?
To complete the backup restoration process, you can simply delete the WhatsApp storage data. This will bring it to the state just after a fresh WhatsApp install, and it will restart the phone number registration and backup restore process. So there is no need to uninstall and reinstall; instead you do this:
- Open the "Settings" app.
- Go to "Apps and notifications → WhatsApp → Storage and Cache"
- Click on "Clear storage" and confirm.
Restoring your messages might have failed if you used Google Drive as a source and the Internet connection was unstable. Here is a solution that will restore messages from a local backup found on SD card instead:
/sdcard/WhatsApp/folder from your old device to your new device by any means.
Install WhatsApp on the new device but do not start it yet. If you did start it already, do the "Settings → Apps and notifications → WhatsApp → Storage and Cache → Clear storage" step from above to let it think it never started.
If you use a custom ROM with enhanced privacy protection settings, such as LineageOS, you have to give WhatsApp storage access permissions before starting it. Otherwise it would recognize a backup but as "Created 1970-01-01, size 0B" and then fail to restore it (source).
To enable storage access permissions, open the "Settings" app, go to "Privacy Permission Manager → Storage" and add WhatsApp to the allowed apps.
Start WhatsApp, register your number, and let it detect and restore the local backup. From here, this is just the regular WhatsApp process to restore from a local backup.
You can manually back up by going to settings -> chats -> backups -> backup
Here is a video screen capture so you can see how to do this.
If that doesn't work I agree with @BuddingPhysicist just uninstall and reinstall.