Payment Unpost says to delete the partial unpost worksheet and I can't find one

I'm trying to unpost a payment. In this deposit, there is only one payment. When I try to save the unpost I get this message:

"This payment group cannot be Un Posted. (6045,12)

Un posting this payment group will  not be allowed as the Partial Un post
Worksheet is NOT balanced. Return to Partial Un post Worksheet and
balance the payment application OR Delete the worksheet."

A. I was not trying to do a partial unpost - doesn't even make sense with only one payment

B. I can't where a partial payment unpost worksheet might sitting.

Has anyone seen this? I'm stumped. Thanks in advance,