Firstly is the charge light on the charger red or green? Red indicates charging, green is not charging.
If the Nomad was over charged or spiked, then run a load on the unit, draw more than 1amp from any of the ports, turn off and on , does the red light come on the charger and or the Nomad red light.
Most common is the overcharge scenario, the unit will not charge until the load is put on.
Take a look that these podcast, they will discuss in detail these situations.
The MPPT (on the red and black poles) connects through the same BMS as the regulate anderson. If you do not have a solar panel to run the test, simply connect a red and black cable to another battery but do not connect to a running car as the voltage will become too high. You can use a jump cable to the red and black poles to your car battery BUT DO NOT RUN THE CAR, just see if the red light comes on the unit and disconnect immediately the red light comes on. The mppt will take about 20 seconds before you will see a charge light.
This is to isolate the issue either the Anderson connection or you have overcharged the unit. If the overcharge reset does not work, there is another test that can be done, but please contact us at technical@renewablebiz.com.au to talk you through additional testing.
Charger issue - it is possible the charger may be faulty, try and charge another battery AGM car battery is fine, you are looking for a red light on the charger which means it is charging.
If you have a DCDC in car charger test the unit on that aswell.