Error by restoring my back-up

[CallMeCurious]

Possibly. See this post that seems to discribe your issue.

Backup file is .tar but pi-hole needs tar.gz

This is because your web browser has "helpfully" unzipped the .tar.gz file when it downloaded, giving you a .tar file. This behaviour might normally be helpful but, as you've discovered, Pi-hole wants that file zipped, so to fix it you can zip it back up again. First of all, rename the downloaded file back to just file.tar. Then gzip it back up with gzip file.tar This will give you a valid file.tar.gz which you can then Restore into Pi-hole in Settings > Teleporter and get your settings back. …