Date won't load with 500 server error on all pages and queries

I am have trouble with data queries, all my pages are retuning this error:
Failed to load resource: the server responded with a status of 500 (Internal Server Error)

here is a link to a sample page:
http://backend.zaprompt.com/untitled.php

What could be causing this. When I test the database connections it is successful and as far as I know nothing on my server was changed.

Please enable the debug mode in Server Connect (as explained here) and make sure to enable the detailed error reporting on your server, so we can see what’s wrong exactly.

I have followed this and turned on debug and the preview window is blank in the browser.

@Edward_Gilbert
Did you check the second part of my message?

Ok, I have done this.

It appears some files are missing from the server. Please make sure to upload everything, especially the dmxConnectLib folder.