We purchased our second Juicebox Pro 40 with NEMA 14-50 plug from Walmart two months ago and just now got a NEMA 14-50 plug installed by a professional electrician.  At first, our Tesla Model 3 charged for a while and then stopped and the charger would show all lights blinking and a single continuous tone.  Now the charger does the same and it doesn’t even start charging first.  I checked the wiring for proper grounding at the outlet and the circuit breaker box, all seems fine.   I plugged in the Tesla's NEMA 14-50 adaptor and used their charger, and charging works fine, although slower at 32 amps.

I think maybe I have a defective JuiceBox Charger. 

What do I do?