Cannot run Year End Wizard due to " Waiting on Bill" boxes checked for Bills that had a prepayment made in a closed year

I have Sage 50 Premium Accounting 2015 and got an error message while running the year-end wizard - It states that there were one or more purchases, dated in the fiscal year I am closing, are waiting on a bill from a vendor. To run the year end wizard, I have to un-check all the bills with the "waiting on bill" boxes checked. 

I was able to un-check most of the boxes in the bills with the "waiting on bill" box checked except the very first bill that had a Dec 2017 bill payment linked to this 2018 Bills; however, 2017 was a closed year, I cannot edit the 2017 bill payment to uncheck the box in this 2018 bill. Please advise me how to fix this issue so I can run the  year-end wizard to open 2020 accounting period in sage 50.

Error message (see below):

Box, circled in blue. are gray out; I cannot edit it due to this bill, linked to a bill payment in a closed year.

Thank you,