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.
If the unit does not charge by the ACDC charger or the DCDC charger (Nomad 10 or 20) amp, check the Anderson connection on the nomad, it is possible a lug in the plug may have pushed back and there is no connection, take a multi-meter and test the voltage at the red anderson if it shows no voltage then it is more likely that the connection lug has come loose. If this is the case you can test the unit from the Black and Red poles unregulated charge poles, if you have a solar panel , just connect it to the poles, and if the red charge light comes on then it is the anderson connection, as the BMS and unit would not indicate a charge light if there was a fault with the BMS.
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 firstname.lastname@example.org 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.