The Mediation Server service has encountered a major call completion problem with these gateway peer(s). Affected PSTN Gateway ...

The Mediation Server service has encountered a major call completion problem with these gateway peer(s).

Affected PSTN Gateway Service Cluster(s): 
%1
Cause: Calls to this gateway failed 5 times with failure final responses.  Check other MOM alerts for more details.
Resolution:
If the failure is MEDIATIONSERVER_GATEWAY_SDP_NEGOTIATION_FAILED (Event ID: 25039), make sure that configuration for SRTP is consistent between the Mediation Server and the GW, and that there is intersection in the voice codec supported on the gateway and on the Mediation Server.  If the failure is due to CALL_FAILURES_DUE_TO_UNEXPECTED_GATEWAY_INTERACTION, there is some internal issue with the gateway peer's link to the Mediation Server (misconfiguration, load) that is causing it not to complete calls.  Please consult the failure reports on the Monitoring Server for more details.