422
providers.refund_unsupportedprovidersRule R4This provider cannot refund this method
The provider that took the payment does not support refunding it through the API. Its capabilities, not paygate's, decide this.
Why the API refuses
WHEN Refund is executed, THE SYSTEM SHALL reject it unless the provider's capabilities include refunding the method; otherwise THE SYSTEM SHALL call the adapter with the resolved credential and the idempotency key and, WHEN the adapter accepts and returns a provider reference, register that reference against the refund for callback routing.
What to do
The refund has to happen out of band — a bank transfer back to the payer, recorded against the payment by an operator. Check this capability before offering a refund button for a method: a refund your UI promises and the API refuses is a support ticket every time.