Okay, yup that sounds like an error is happening and preventing them from loading. What are your system specs? Also if you press Ctrl+D a debug window should pop up, can you let me know if you see any errors in the console?
So I get the same debug error on my laptop as my desktop via the debug: The specified value "#0000 does not conform to the required index.html:205 format. The format is "#rrggbb" where rr, gg, bb are two-digit hexadecimal numbers.
Curiously though, my desktop has slightly different specs than my laptop but the laptop CAN change fonts with no issue. Laptop specs are : AMD Ryzen 7 5800H 3.2 GHZ with 16 GB ram and Geforce RTX 3050 Laptop GPU
Desktop: Ryzen 7 3700 3.6 GHZ with 16 GB ram and Geforce 3060 GPU
I'm at work until tomorrow so I cannot get my DXDIAG for my desktop until then