I received the same error while working on my 2021 taxes. It turned out the problem was in a Form K-1 where I had a box 14 with Foreign taxes paid. There is a field called "Gross Income Sourced at the Beneficiary Level". By default TT had 0 there, even though it could have easily computed it from the information supplied in the K-1. After I put in the proper amount there was no error later in Form 1116. Note I had did this by restarting with a copy of the Tax Return saved before starting work on Form 1116. So I'm not sure if it's possible to easily fix the error once it has occurred.
