You indicated that perhaps your host has changed something? If so, contact your host and explain to them HTML 5 isn't working on your site. I don't know code, but I had a look at your page source and the code you changed does look correct. I'm not too sure what the issue is.
Do you have anything funky in your htaccess perhaps? Maybe it's mod_security. That's all I got. You could have your host check the page source, and if your host can't help then I would look at hiring someone from Fiverr who knows web code.