This can happen if you don't fully seat the plug in the car's charge port. There's a certain point where it's in far enough to make solid contact, but not enough for the car to be able to lock the plug in the port. In that case, the car will still charge, but only at 16A. (Presumably that's the maximum safe level in a situation where the plug could be pulled out at any moment without warning.) When this happens, the charge port will be orange rather than green.