Sage 300 Purchasing Module

Having trouble getting answers from Sage Support.  After I enter a credit ap invoice in Purchasing / Task / Enter Return Authorities and post, the credit is not showing up in the Reports / Status / Order Details by Job report.  Then I am prevented from entering a new AP invoice because there is not enough money in the PO.  So when entering a credit invoice, the system does not put the money back into the PO?   How does this process work?  I am referring to a August 2021 Purchasing User's Guide, and the wording is totally different.