Installing Font (Cabin) doesn’t seem to work

Dear Community,

I migrated a WordPress Website to twenty twenty five.
My client would like to have “Cabin” as headline font.

So I installed it as custom font under typography.
No error messages appeared.
However the font is not used.
Even in the preview it seems to be displayed in “sans-serif”

Debugging:
I edited the CSS in the browser
before:
--wp--preset--font-family--cabin: Cabin, sans-serif;
after:
--wp--preset--font-family--cabin: Cabin;
Result:
The headlines change to Times New Roman.

That’s an indicator that the font is not available at all.
My client and I had massive problems with the fonts since either of us different fonts on desktop and mobile devices, so instructions got quite confusing.
Only today I figured that there is this technical problem.

As far as I understand it, the fonts should be copied to the local webspace.
Where should they be stored so I can check?
Has anyone else had this problem before?

If you need any more information, just ask…
Thanks in advance

The page I need help with: [log in to see the link]