Form not showing up consistently

Are there any known plugin conflicts with Boxzilla? I’m trying to use it in conjunction with M4WP to display a pop-up opt-in form for my client’s site. I’ve been testing in incognito browser windows and the pop-up window isn’t coming up consistently. I’ve got it in test mode right now… would that make a difference?

The page I need help with: [log in to see the link]