Supplier field value on Redwood Self Service Procurement not recognised on Visual Builder

Summary:

On Redwood, how to make a DFF field mandatory based on Supplier name?

Content (please ensure you mask any confidential information):

Hi Support,

On the Fusion Procurement Redwood page, I am making fields mandatory via Visual Builder.
-> Create line on Purchase Requisition screen > Click on profile > Edit pages on Visual Builder Studio > Configure Fields and regions.

I have created a form rule with the following conditions to make a DFF called 'DFF1' mandatory.
Please find below conditions and outcome

If Supplier (purchaseRequisitionsLine) is null -> Outcome is successful, DFF is required when field is null
If Supplier Site value is 'SITE 1' -> Outcome is successful, DFF is required when site is SITE 1