cant request override when submit purchase order

Summary:

we create budget and allow override and i enabled "Funds Override Approval" in manage purchase document approval and also the user that create PO has catalog administrator , procurement manager and buyer and advanced procurement requester roles. but also i cant request override when submit PO only a message appear that funds failed. "The distribution failed funds check."

so is the user need a specific role or privilege's to can request override?

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