How to resolve error "A supplier is required for the supplier site or the supplier site is invalid.

Summary:

New supplier site was created and tag as Ordering and Remit, Purchasing and Pay as site purpose. The supplier and site is in active status. 

Existing purchase agreement was updated to use the new supplier site. 

However, error is encountered when creating requisition for items under the same agreement.

Error: LineNumber 1: A supplier is required for the supplier site or the supplier site is invalid. (POR-2010934)

As per checking it looks the configurations is correct and active. We would like to check for ideas how to resolve this error.

Is there a process that should be run when updating an Agreement and Supplier to reflect changes?