Try joining from a computer - not from a phone. Sometimes I find the sites don't work well on phones to sign up.
Call the store during Mon-Fri, non-rush hours, and speak with the GENERAL manager.
I joined using Chrome, IE did not work. If you still can't get it to work, try going to the restaurant and scanning the QR code on the tables. It is a direct link and will work
Check facebook. Often they have links to clubs in groups
Thanks! Your answer is awaiting moderation.