First I would advise you to check the PO-I-F Report to confirm that DBA recognized your matching the invoice to the purchase order in AP-C.
 
If so, what I usually do in this situation is re-enter the invoice in AP-B as a manual invoice, and the GL account to be charged is the Received/Not Invoiced GL.  
 
This happens to me a couple times a year, not sure why, but it usually clears the PO-I-F report, but the transaction only partially updated all related files with AP Aging usually the only one not updated.
 
Lynn could probably advise you how to manually edit the proper files in Maintain DataBase.