While trying to call in to a conference from an external PSTN connection the error “Sorry, I can’t seem to connect you to your meeting…”

Error Message
S4 traces on snooper revealed a “foreign gateway” IP address been called by the Mediation server.

The default Gateway in Topology Builder was an old (decommisioned) SIP connection (aka “foreign gateway”. Changed that to the gateway I was actually using to call out on – solved!