Turn off the machine and look for a cause. Try to turn the back handwheel. Remove needle plate and clean thoroughly. Look behind bobbin case assembly for thread. Oil liberally. After oiling, try once again to turn handwheel. Rock handwheel back and forth to free up jam. Oil everywhere and run machine un-threaded on a medium constant speed for a short while to lubricate everything.
Gammill- remove side front panel and look for thread caught around shaft beside handwheel
If there is no jam, check that the needle encoder is intact and that all plugs and wires to it are secure. Also check the phone connector to the CPU board. Check the cords as well for damage. If cords or encoders are damaged, they need to be replaced. Cords can be purchased from www.quilttech.com. Encoders must come from your dealer or Intellistitch.