First up, dissconnect the base from the PC. Unscrew the locking collar and ensure you have correctly keyed the plug from the grip into the socket on the base. Once keyed correctly, push it in firmly, place the grip on the base and tighten the knurled locking collar. Then run up Simappro and plug your base back into the pc. Also ensure that the USB connector is firmly seated.
Do all your throttle switches work in Simappro?