I just wanted to update this.
The issue turned out to be a network gateway between the Mitel and the Vocera. We found that pings were not passing and the gateway port was frozen. The port was Shutdown / NoShutdown and traffic was passing again, also the Vocera system is answering now.
So far as the CPN Substitution that was in programming, none of us could figure out why it was there, except if it was leftover from some previous programming. So I removed it and all it fine.
Thanks for the input on this, as it ended up verifying what I thought, the "Mitel" was fine, it was network. Even though the Vocera support could only point to the Mitel.
Thanks !