We had to do workarounds and such years ago, but this is 2020 now, and you can just buy the perfect almost official looking TT-30 adapter from EVSEAdapters, and you're good to go. It will automatically announce the appropriate 24A limit to the car too.
Any of these kinds of 14-50 to TT-30 adapter plugs you find in RV supply or camping supply places just will not work for electric car charging because they are wired the wrong way for what an EV needs.
@DCGOO points out the problem. RVs are not actually trying to use 240V, which was a surprise to me when I learned it. They just have a lot of 120V loads that they need to spread out across two different circuits, so they don't overload something. So those pigtail adapters take the 120V hot line from a TT-30 outlet in the pedestal and put it on BOTH "hot1" and "hot2" of the 14-50 receptacle end. An RV is only looking for 120V connections from either side to ground anyway, so that's fine--just less total amps to work with.
But an EV charging unit is trying to read a voltage difference across hot1 to hot2, and when they are hooked up to the same wire, there is 0V, so it just sits there doing nothing.
So you can find some of these kinds of adapters that are specifically marked for EV charging that wire it differently inside in an "improper" way to put the 120V and ground across those two hot1 and hot2 pins to make it work. But those don't tell the car to proper current limit, so you would have to remember to manually dial it down, so I don't really recommend those. It's kind of unnecessary risks since there is a better version of adapter available now.