It is most likely a simple connection issue.
1. First unplug and replug all of the connections on your kit including all of the Main Wiring Harness connections (display, throttle, brake levers) and all of the Motor lead connections with the Battery and Speed Sensor. Make sure no pins are bent/damaged on any of the connection plugs and line up the arrows and pins when reconnecting everything to ensure proper connection.
2. If Step 1 does not fix the error, check that none of the wiring on your QuietKat is being pinched, especially the cables coming from the controller. Check to make sure that none of the wiring on your is too taught and is pulling the cables from the controller.
3. Open up the controller from the motor core and unplug all of the controller plugs and replug them again ensuring there is no silicone interference and everything is properly connected.