Everything else is functioning on the car? There are no warning lights on the dash
Go to the home screen of the Garmin Tread. Navigate to the Vehicle Integration or Apps menu (this is where your gauges and KECS controls live).Look for a Diagnostics or System Status sub-menu. If the CAN bus error is isolated to a specific module, it will often state exactly what it lost contact with (e.g., "ECU Communication Lost" or "Suspension Module Timeout"). Then you will have to check fuses for what it lost contact with.
Could get lucky and it is simply a loose wire/cable. Remove the GPS and then unbolt the holder and check to make sure all the cables/wires are connected and not loose.