Hi, I took a look. I'm not sure if this the template or community builder, there is a validation error on your site coming from the CB code and maybe it's just not jiving with the theme.
Either way, I was able to fix it. Go into your template.css file, find line 432 - it's all the codes for the input buttons, remove or comment out float:left; - the float is making the button appear behind another element, that's why you can't click it. Keep in mind this will affect all the input buttons on your site, so I'll put a code below that you can use if it messes up other pages.
At the bottom of your template.css, add this code. The first line brings the button to the front, the second will fix the issue from above:.cb_button_wrapper {position: relative;z-index: 9999;}
.contentpaneopen .cb_button_wrapper input.button{ float: none;}
Hope that helps.