Hey, thanks for the invite but you have to fix the join button or you won't get any new members. Most people trying to join don't leave comments so you can't just send an invite to everyone who comments. You won't get many members that way.
Okay! First go to Admin Area Then Manage Members Click Members From On Home Members keep reading till you find "Join Requests". The default option is "Are Not Allowed" which you need to cange to either "Are Automatically Approved" or "Are Subject to Vote..." Press "Save Now"