Pop Up – show only once not working

I have been using Modal Window for quite a while and love it. It’s always worked well. For the last few months I’ve had a problem with one pop up that I have set to Show Only Once with a reset of 2 days. It used to work fine, however now it pops up every time that page is loaded. The strange thing is, if I am logged into the wordpress admin site and run it, it’s fine. But when logged out (which means any customer coming to the site) it pops up constantly on reload.

I have tried clearing the site cache, and clearing my browser cache but nothing helps. Any ideas on what I should try?

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