Check your connection: Make sure the truck’s ignition is on. Restart the engine. Then, restart the device. Check to make sure the blue indicator on the back of your HD 100 device is lit.
You can also try unplugging the device from your J-bus and re-plugging it while the device is powered off. If you still continue to encounter an issue, call Rand McNally Customer Support at 1-877-446-4863.