I just got this error multiple times when trying to charge our new X with the new-cheaper-style mobile connector at 240V. It did work a few times, but failed many more times. It also failed a couple of the few times I tried the new connector on my S.
Using the same mobile connector at 120V works just fine. Our wall connector at 240V works fine too; as my other mobile connector, and a J1772 EVSE.
There is nothing wrong with the 240V outlet; I have used it to charge my S and Roadster for years, and other chargers I plug in there work on the X.
A tech is stopping by tomorrow so I'll ask. It could be the new connector is just sticky and despite my best efforts (I am aware that new ones are often sticky and need to be forced in) it is just not always going in all the way.