27" Thunderbolt Display not working

Hi. I'm asking this regarding my work Mac. It's a 2 x 2.66 GHz 6-Core Intel Xeon Mac Pro running 10.9.2. It's connected to a virutall brand new Apple Thunderbolt Display (27-inch) as well as an old Cinema HD display (23-inch DVI (1920 x 1200)). Cinema display works fine. The Thunderbolt display doesn't display anything from the Mac Pro. It works fine with a MBP. Tried both Thunderbolt ports, reset SMC and PRAM. Tried restarting with the Cinema display unplugged. Tested the camera via Photo Booth, no camera detected. Displays in System Prefs only shows the C-HD. Monitor is able to supply power via USB. Does anyone have any ideas? Thanks