Does it work if you register your EX90 to your CUCM?
if so, there could be an issue with your trunk between the CUCM and the VCS, or with your firewalls or network in between the devices (things like packet inspection, blocked ports, WAAS, ect can all have an impact).
Note: This discussion would be better placed in the TelePresence section of the forums where these devices are more actively discussed than in the Video Over IP section you have posted in. I suggest that if the replies you have here have not helped you track down the cause of your issue, that you move your discussion over there to gain visibility by those of us who specialise in there devices.
Wayne
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