If users are unable to join a Lync conference via the IVR or using a dial plan rule that resolves to “Lync”, the first thing to do is to verify that the “Lync Edge” settings have been set up as per the deployment guide - the same mechanism is used to resolve Lync conferences as is used to find the Edge server. The Meeting Server must query the Lync FE server to find both of these.
If this fails, an message will be logged in the event log to say that the conference ID cannot be found;
lync conference resolution: conference “1234” not found
This may mean that the conference does not exist, but there are also other possible causes.
If SIP traffic tracing is enabled, there should be a ‘SERVICE’ message sent to the Lync FE server just before the above message is logged, which should be replied to with a 200 OK. Check that this message is sent to the correct IP, which should be that of a Lync FE server.
If this message is not sent (it does not show up in the logs), then it is possible that the callbridge is unable to find the Lync server using a DNS SRV lookup for the _sipinternaltls._tcp.lyncdomain record, and so does not know where to send it. Enabling DNS tracing and retrying should confirm this. However this can also happen if the Lync Edge settings have not been configured on the Meeting Server.
If the Service message is sent but the Lync server replies with “403 unauthorized”, then the most likely cause of this is that the local contact domain in the outbound dial plan rule for this Lync domain is not set correctly. It should be set to the FQDN of the Meeting Server, which should be the same as the FQDN supplied in the CN of the Call Bridge’s certificate.