Getting default Apache2 Debian default page

I had to shut down and restart my server. Now if I navigate to my site, the default Apache2 Debian page comes up ('it works'). What happened? How may I restart the 'XenForo service'? All the endpoints that used to live are now down (404 Not Found).
The default Debian page is index.html?
Do you have a index.php in your folder?
I understand that.. but my XenForo forum has like totally disappeared. The files are still in the directories, its just none of the endpoints are working.

There is no such thing as a Xenforo service. It doesn't run as a service.
I understand. What caused my problem then? Why is my apache configuration file not serving my XenForo forum anymore?