"You can't enter the invoice lines because the invoice header is incomplete."During Invoice Creation

Hi,

When trying to create an invoice in the Payables module in our TEST environment, we are receiving the following error:

"You can't enter the invoice lines because the invoice header is incomplete.  Enter the required information in the invoice header before entering lines."

The header appears to be complete and has been entered the same way as we always have. We have even tried different suppliers, business units, adding attachments, etc., but we still receive the error.  

This issue is also occurring in our DEV1 environment.

We can still successfully create invoices in our production environment, but we believe that this is because we have received release 26A in our lower PODs but not in PROD yet. It is scheduled for PROD this weekend (2/20), so we fear that this will become an issue in production soon.