Voucher Build With No Vendor ID

We're upgrading PeopleSoft FSCM from PUM 31 to PUM 38, and PT 8.57 to 8.58. When we build a voucher from the staging tables, it goes to the quick voucher tables with the message, "Invalid supplier for Purchase Order".

The data we're receiving doesn't have the vendor ID populated, but it does have the PO ID, and this hasn't been an issue in the past. I tried it in one our non-upgraded environments and it loaded correctly. The supplier on the PO is valid and active in both environments.

I found Doc ID 2762846.1 and was wondering, is the vendor ID requirement new since PUM 31, or is there something else going on?