The Mediation Server service has encountered a major connectivity problem with the Front End. Front End FQDN: %1 Cause: ...

The Mediation Server service has encountered a major connectivity problem with the Front End.

Front End FQDN: %1
Cause: MEDIATIONSERVER_PROXY_OPTIONS_FAILED (Event ID: 25053) was recorded 5 times.  Check other MOM alerts for more details. The MEDIATIONSERVER_PROXY_IP_NOT_AVAILABLE (Event ID: 25072), MEDIATIONSERVER_PROXY_TLS_NEGOTIATION_FAILED (Event ID: 25071) are examples of events that signal connectivity error conditions with the Trunk peer.
Resolution:
If the failure is MEDIATIONSERVER_PROXY_IP_NOT_AVAILABLE (Event ID: 25072), make sure that the correct listening IP and port for the Front End have been configured in the PSTN Trunk object in management store and that the Trunk is up and running and able to accept incoming connections from the Mediation Server.  If the failure is MEDIATIONSERVER_PROXY_TLS_NEGOTIATION_FAILED (Event ID: 25071), make sure that both the Mediation Server and the Front End are configured for TLS and that the CA for the Trunk's certificate is the trusted certificate path on the Mediation Server and the CA for the Mediation Server's certificate is in the trusted certificate path on the Front End.