Hi! I am having a similar issue with a custom font for h4. The font I am trying to use is a font in Squarespace (Cubano), so I didn't add a source url. It appears to be working perfectly fine when I am editing, but I realized it is not actually working when opening the site from a different browser.
Below is the CSS I put in:
The website is https://raccoon-saffron-2c5h.squarespace.com
I also tried adding !important in there, but that also didn't work. Any ideas?