Lately there seems to be a rash of problems with mobile connectors using the Tesla 14-50 NEMA adapter. My suggestion would be to see if you can plug your setup (minus extension cord) into somebody else's known working 14-50 outlet and see what happens. Alternatively, you can try going to your local Tesla Service Center and see if they have a 14-50R and test your equipment. If it also does the same, swap out the NEMA 14-50 adapter with one that is known to be good and try again.
You can try disconnecting the NEMA 14-50 adapter and re-insert it (hard) into the mobile connector and then try charging. It might just be a bad connection with the adapter.
Another possible troubleshooting item, but it would cost some money, would be to get your hands on a 14-50P to 14-30R adapter cord and use a 14-30 NEMA adapter with your mobile connector. What I'm suggesting is to not use your existing 14-50 NEMA adapter with your mobile connector and see if the problem goes away, If it does, then your 14-50 adapter is the problem. If it turns out you still can't charge, then it could be your mobile connector.