Buyer role not working correctly when delegated using the vacation role

Summary: We have one person in purchasing who is assigned the buyer role. From what I read, there is no way to assign more than one person this role. Said person is on PTO this week with vacation setup to delegate roles to another person in purchasing. The vacation rule seems to be working correctly and Oracle is delegating to correct person.  The issue is with the PO approval status.  She can get to the point to build the PO, but it won't finish and issue, because it says it's pending approval. Is there something that we may be missing?