I’m not sure what the specific issue could be, but your site could use some performance optimizations at some point. I ran some tests from California and your site loads in ~15-20 seconds.
I used GTmetrix, Pingdom and WebPagetest from various locations on your site. You seem to have a lot of external resources which are adding to the overall load time. I can help you troubleshoot a bit more later but check out the performance and see if there’s anything obvious that stands out. During my tests your site wasn’t ‘down’ at all, just loading a bit slow.