Server isn't responding

At 8 a.m. this morning our website at “www.chathamorpheum.org” would not open; message back was “server (at this url) was not responding.” An hour later, it came up and worked fine. I then logged in about 10:30 a.m. via WordPress to update a story, and had no problem. But now the site is “down” again, same message (both from Safari and Google Chrome) that “the server where this page is located isn’t responding.”

This is a site for a brand-new non-profit movie theater … no website access will kill ticket sales. Help!