On a given "group" page, users cannot click on the "join group" or "invite friends" button.
Looks like your template's css is actually messing with the group title causing it to cover the button. You can fix this by adding the block of css codes below into your template's css file,
You're welcome. Glad to hear your issue have been resolved.
If you have anymore question, please don't hesitate to ask us and please create a new ticket. I will mark this ticket as resolved.