The Microsoft Exchange Unified Messaging Call Router service failed to exchange the required certificates with an IP gateway ...

The Microsoft Exchange Unified Messaging Call Router service failed to exchange the required certificates with an IP gateway to enable Transport Layer Security (TLS). Please check that the gateway is configured to operate in the correct security mode. If the gateway is required to operate in TLS mode, check that the certificates being used are correct. More information: "%1". Remote certificate: %2 (%3). Remote end point: %4. Local end point: %5.