Backup to Google Drive - Disabled by your admin. Why does my device show is? It's preventing me from restoring my backed up apps.
From Google Product forums , this has been widely reported by Nougat users and is a false alarm

Reply from Google help yesterday (08 Aug)


  We just received a feedback from the Android team. The error that you are encountering is actually being displayed by accident for some Android Nougat users. It has no effect on your data being backed up or not. The status of backup being on or off is correctly captured in the first 'Backup &amp; Reset' screen, and can be controlled by the user. For now, you can safely ignore the error message until a fix is rolled out by the Android team which should be around September 21, 2017.


(Emphasis Supplied)

Other users have reported that they have been able to restore despite the warning