I have this occasionally happen with one particular client.  We can see the receipt in Receipt History, but the Qtys on the LINEs still appear to not be received (but there is a total received amount on the Total tab).  I have to DFDM the qtys, then pull up the PO, save it, and it changes its status to complete when saved.  I've tried to figure out what they are doing differently, but all looks OK.

There are several reasons this can happen, the most common being the invoice was done in AP instead of PO.  See Article ID 222924450018964  How to complete or resolve backordered purchase order on the Sage 100 knowledgebase.

There are several reasons this can happen, the most common being the invoice was done in AP instead of PO.  See Article ID 222924450018964  How to complete or resolve backordered purchase order on the Sage 100 knowledgebase.