LiteSpeed "error" message

[endresol]

I have used Fluent Snippets on a few sites, with more or less no problems.
However now I have big problems for a new sites I just created.

I am trying to add a snippet for loading fonts that I also have used before. I am copying the code from the other site, where it works, to the new site and get a black box with the following text:

Proudly powered by LiteSpeed Web Server
Please be advised that LiteSpeed Technologies Inc. is not a web hosting company and, as such, has no control over content found on this site.

Under that box I can see a yellow box but not any error message.

I have disabled more or less all plugins, and still get the error. Is this LiteSpeed something you, Vue.js or other frame know about?

On this page you can find the code I am trying to add:
https://www.altmann.de/en/blog-en/code-snippet-custom-fonts/

Thanks

Endre

[endresol]

So, looks like it is my host that is using LiteSpeed, sorry.
Any ideas why it works on one host and not another?