Working installation broke and new installation failed

I’ve tried several things to get my nextloud server up and running. I’ve have had a running server but it’s not functional anymore.
Whenever I’m trying to access the server I’m getting an almost empty page with the logo and thats it. No Login or anything else.
Funny thing is that my previously working server stopped working with the exact same symptoms.
There are no errors in the logs and I don’t know what to do.

Please help.

Fixed the issue.
Problem was the “Cloudflare Rocket Loader”…
Disabled and eveything works again.

What is that?

Some feature of your hoster?

This is some feature of Cloudflare that was supposed to make things faster. But it seems to break things.