I haven't heard of this one before. While you may be able to wait for other cars to open the gate then follow in, that is unsatisfactory. I would start by asking them nicely (verbally and in writing) to replace the clicker or give you the new code. There may be a mediation process in place which should be considered and may even be required in your jurisdiction or in your CC&R's. If you're really mad (and I would be), and have extra money to spend, a civil lawsuit for an injunction, false imprisonment, breach of contract, etc., all may be possible, seeking a temporary restraining order to gain immediate access.