Since you have IP connectivity between the Mitel servers, it is likely a config issue with the Mitels. Do they use H323? If so, are they configured with call routing rules pointing to the far side server as a gateway for the appropriate number? Or is there a gatekeeper defined? If so, where is the gatekeeper?
Once you get the calls working you will want to be sure you have QOS configured on your routers and switches, but that is a voice quality concern, and will not stop the calls from being placed.
Ok - I finally found out the issue has been resolved. The Mitels have been configured by their local telco, and they had a tech go over from the telco and verify the Mitel configs. Turns out that the configuration needed a little 'adjustment'...
They're working fine now... and all along I thought I'm missing something.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.