Message SAP XS643 - Currently no delivery to &, as error occurred during encoding/signing

Diagnosis
The message could not be delivered to recipient &V1&, since it could notbe encoded or signed by the security proxy. A possible cause for thismay be a missing certificate.

System Response
Processing was completed normally.
Additional information of the used node (if available, in the systemlanguage of the node):
V4

Procedure
Attempt to resend the message at a later time.