gdeal, let's start with the basics. I believe you are saying you get no water when you hit the "flush" switch.
I have a Thetford cassette, and I don't know about a controller card. I believe mine only works from opening a valve, and letting the pressurized water flow. Is your water pump on? Do you get water from other faucets?
If your other faucets work, look at the wiring behind your flush switch. Make sure all are connected. If possible, check for current at the wires as they come into the flush-switch area. I wouldn't do anything else until I made sure there was current getting to the switch. Go from there with circuit checking.
Good luck!