Check Your Android Right Now to See If Your Automatic Google Backup is Broken
Android devices won’t notify you if the Google Drive backup fails or stalls this way, so tons of other Android users may be experiencing the bug without even realizing it. The only way to confirm your Google Drive backup isn’t working is to check your system settings. Go to Settings > System > Backup, and if the “Backup” button is dimmed out and the various data categories say “Waiting for backup,” then—lucky you—you have the bug.
Source: Check Your Android Right Now to See If Your Automatic Google Backup is Broken