WordPress/Buddypress theme has suddenly stopped working [closed]

Your site has some issues:

  1. There is no default theme stylesheet present in the page markup. I can see several plugins loading their own styles, but none for the main style.css.
  2. The page is broken. A view-source shows it cutting off at the bottom. There are no closing </body> or </html> tags.
  3. Your server is returning a 500 Internal Server Error message along with the regular page request, so something is breaking on your server.

Unfortunately, all three of these point to some significant issues on your server and something that requires serious hands-on support. As this is not a support site, I’m closing your question as off-topic and suggesting you ask in the official support forums instead. I just wanted you to have a few details for debugging first.