Request to Make “Identifying PO” Field Mandatory in Sandbox Environment

Issue Description:

Dear Oracle Support,

We have a business requirement to make the “Identifying PO” field mandatory in the Payables module, specifically when the Invoice Type is set to “Prepayment”, within our Sandbox environment for testing purposes.

Scenario:
When users select “Prepayment” as the invoice type, the system should enforce the “Identifying PO” field as a mandatory field before allowing them to proceed. However, we were unable to achieve this behavior using EL Expressions via Page Composer.

We attempted configuration through personalization but the EL condition is not triggering as expected. Therefore, we require guidance on the correct approach — whether through Groovy expressions, Page Composer rules, or personalization logic.