the LED you see acts as a power/code LED
if there were any active codes in the controller it would be flashing a code
if it is on steady then no codes are present
if it has a premium BDI guage it may show battery status and display codes in the hour meter area of the guage also.
When you power the unit on watch the bdi guage and see if any numbers come across it while it's powering up.

the fact that you have a light on the controller 'on' means it is getting power. Have you checked the brake switch at the base of the handle on the drive unit? Most units will not do much of anything until the handle is pulled down to activate the system in drive mode. If there were any problems in the tiller card there would be a code. Go back and double check control fuses, brake switch, and you may want to check the power fuse on the buss bar if it has one. Sometimes they look good and even ohm out good but under load they dont work, IE: partially blown in a way you can't detect with a meter or see.

i'm sure there may be other things to check but these are just a couple off the top of my head...

Other than that i'm at a loss