This is our dimmer set up at Newberry.  Many theatres have a similar set up--but may not use the "patch panel" as we do.  Since we have retrofitted a system with 150 something circuits to be run by 96 dimmers---and we usually run dimmer per channel---the patch panel was kept to allow us to use ALL the circuits in the theatre by plugging or unplugging the particular circuit into a particular dimmer.

One thing to check if you can not get a circuit to come up is to determine if it is STILL the circuit patched into that dimmer!