Q: iCloud backup failing since 9/25

I have been unable to backup my iPad (Air MD788LL/A - IOS 9.0.2) since 9/25 (so iTunes and the iPad tell me).

If I open the iPad, select Settings/iCloud/Backup - Backup now, I get the message:

"The last backup could not be completed."

iCloud Backup is turned on.

No logs or other error information I can find.

As best I can tell everything else is working as expected.

Note that I do have 2-factor authentication turned on.

I've turned off iCloud Backup and done the partial backup to iTunes via sync with no apparent problems.

I've power cycled the iPad

At best I get partial completion - the iPad tells me about 1 minute remaining before it fails again

with the same error message.

Any guess what is failing?

Is there a log file anywhere to tell me what is failing?

NOTE that none of the categories provided by Apple are even vaguely appropriate.