Custom cssclasses not applying to notes

What I’m trying to do

I am trying to get custom css classes to apply to notes. I add the cssclasses property to my notes and add my css class but nothing happens. I have tried this with my own css snipets as well as others and despite showing the class being added in the consol, nothing changes.

However, if i write the css outside of a class it then applies no problem.

Things I have tried

I did manage to get it to work once but I have been unable to recreate it. I have tried it in a new vault with no plugins but still nothing works. the css snipet is enabled in the settings. No error is raised either.

Here is the other css snipet i tried. It worked once but then stopped functioning aswell:
GitHub - CyanVoxel/Obsidian-Notebook-Themes: A Series of Notebook Theme CSS Snippets for Obsidian.

My own CSS called via cssclasses is working fine. The linked snippet seems alright as well (I only tried a few classes).

Please share some examples and what you are typing in for cssclasses. Maybe someone can spot something.