I have tried to charge via a free CCS charger at a local GM dealer in Florida but it has never worked. I had assumed it was a faulty charger but now discovered it will work if you follow a certain ( somewhat illogical procedure IMO). Previously I plugged in everything and hit start on the CCS charger control panel. It always timed out saying communication error.
What I do now is connect the Tesla CCS adapter to the charger cable, hit start and then after a few seconds plug the CCS adapter into the car. Charger communicates fine, shows the level of charge and starts charging. Not a fast charge, 19 kW , but price is right and I go for a walk, coffee, etc.
No idea why this works but it does.