The problem was apparent, when a call was made inbound to the on premises SfB Server PSTN Dial-in access number.
In this deployment, the customer had already configured the SIP trunk and calls inbound and outbound to and from end-user assigned numbers were working fine, two-way audio, good quality and calls were staying up without any issues.
I have recently been troubleshooting an issue a customer had been facing since installing a SIP trunk from a UK Provider in preparation for a migration away from older ISDN circuits.
