At times, a pending invoice will not show the options to Approve or Post. This is due to a Microsoft bug that appears to occur when a pending invoice is deleted from the Pending Vendor Invoices list - at times, the pending invoice does not fully get deleted.
To workaround this, the pending invoice must be deleted and then an new invoice created.
To do so, follow these steps:
1. Navigate to Accounts payable >> Inquiries >> History >>Invoice history and matching details
2. Filter for the PO#
3. Select the invoice number
4. Alt+F9 key to delete
Then the invoice will be able to be recreated.