Problems backing up iPad to Mac or iCloud

I have an iPad Pro that I have been unable to back up either to my Mac or to iCloud for over a year now. I have all the latest software on all devices. With the Mac it says that “An error has occurred” and with iCloud I get “The last backup could not be completed”.

I can backup both my iPhone and a different iPad to both the Mac and iCloud so I conclude there is no problem with either my Mac nor my iCloud account. One “interesting” symptom is that when I look at Manage Storage under iCloud settings then look at Backups, it shows that there is “apparently” zero data to back up on all 200 or so Apps, which is blatantly wrong. I have reinstalled the iPadOS many times, but of course don’t have a backup file with which to do a full restore. I have removed Malwarebytes, and tried everything I can find in Discussion groups. Can anyone suggest a fix?