On Android, it can sometimes take a long time to load backups (anywhere from a few minutes to a few hours).

Backups sometimes do not appear in the cloud backup loading menu, but this does not mean that they have been deleted; they just take a long time to load. 

Unfortunately, the only solution is to wait, as this depends on Google. Make sure you don't start a new game on the same save slot, otherwise you'll erase your progress forever!