We recently upgraded our UC to UC520-4.2.9 EA, incomming calls worked just fine.
Anyways our UC is behind an ASA no changes have been made the ASA
A debug of the sip messages shows that after the inital invite message the UC returns a 500 Internal Server Error with Reason: Q.850;cause=63
shows a "63" as:
Service or option not available, unspecified - Typical scenarios include: Service not available. - Reports a service or option not available event only when no other cause in the service or option not available class applies.
I am lost on how to debug this one. any ideas??