Took a few days to get to the bottom of this.
Root of the issue is people could make pstn calls through our IPOffice via Lync when in the office, or on the vpn, but if connected over the edge server (for instance if using DirectAccess) – no beans. Basically the call is placed and when it is answered there is ten seconds of silence and then the call drops – no sound at all.
After much digging i eventually came across these technet forum posts:
And this one
When i looked in the topology on our mediation service, i saw the below (this is not my image but the technet forum posters), the edge server basically “Not Set” on the mediation service.
Somewhere/somehow it had gone missing on this particular front end server.
In order to correct this i followed Kressmarks solution on the second link above:
and quoted below:
We then used the following command, clearly inserting your own fqdns for mediation and edge servers:
Set-CsMediationServer -Identity “MediationServer:standard.kressmark.com” -EdgeServer edge.kressmark.com
Once you restart the FE and mediation services, calls resume and the correct info is reported.