No unique mandate activated for customer &

What causes this issue?

A SEPA payment method requires an active mandate. However, for the
customer, there is either no mandate active or more than one mandate
active.

System Response

This is a warning message. You can still continue processing.

How to fix this error?

Check the mandate.
INCLUDE 'CUSTOMIZED_MESSAGE_INFO' OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.