I just recently encountered the same error message in QB 2021 Desktop, which did not make sense since all the Items in the Item List had valid Expense and Sales accounts. The error message was occurring for the most frequently used Items when entering either an Item Receipt or a Bill.  So, I knew it was some sort of data integrity issue.  First, I verified and rebuilt the file, which did not solve the problem (and I thought it would).  There were no errors from the rebuild, which surprised me. Realizing I had to somehow reset the Expense and Sales accounts for the affected Items, I then edited each Item, changed both the Expense and Sales Accounts to any different Expense & Sales account, said Yes to changing history (to fix data integrity issues), and then re-edited each Item to change the Expense and Sales accounts back to the correct ones, also saying Yes to changing the history.  There may be a faster way to fix this, but this worked for my client.  They could not receive against the majority of their PO's due to this error.