Hello, I'm having the following problem: Lots of H5P-content in my WordPress, so far everything is working fine. But now I am trying to do the following: embed published H5P-elements via iframe directly into the index.html of another Website. Problem: Some elements show up and work just fine and others don't ("content unavailable") without any pattern I could recognize. I tried to open the element's adresses directly in the browser and could exactly reproduce the behavior. Not working elements get the error message, working elements show up. The URL is like this:
~~~
https://my-site.net/wp-admin/admin-ajax.php?action=h5p_embed&id=9
~~~
I just change the "id" at the end to choose another h5p-element.
All the elements I tried are already published on wordpress and should therefore not have any issues with autorization. But what do I know?
So I'm a bit lost here. Any kind of advice would be much appreciated.

If you open browser dev tools (f12) on a page that doesn’t work, what error do you see in the console and/or network tabs?
h5p_embed isn’t a core WordPress thing. A quick Google shows that it belongs to Moodle – are you running a plugin for it? If so, you need to content the developer of the plugin.