Please bear with me as I'm not technologically gifted (nor, often, competent). I have googled this problem as best I can but to no avail.
When I started scrolling through the 'Find More' fonts list this morning, a good number of them were not previewing. After some experimenting, these are (I think) the pertinent details:
The issue is only manifesting on the 'Find More' list, not the 'Fonts' list;
Every font family up to 'Karmina' is previewing with no problem;
Thereafter, I estimate 80-90% of families not to be previewing;
When I click to see the fonts within a family that is not previewing, they all individually preview with the exception of the regular font (I assume this has something to do with the lack of preview beforehand);
This issue is affecting font families I have activated as well as those I have not, but it is not affecting them when they appear on the 'Fonts' list as opposed to the 'Find More' list.
I hope this makes sense and I would be extremely grateful for any guidance. Many thanks in advance.
I also have some massive issues with fonts on the latest version of Illustrator on Big Sur and Apple Silicon M1 (16 GB RAM). The preview is extremely slow, I have spinning beach balls for 2+ minutes when trying to change the font. So I switched off font preview and it still takes forever (doesn't matter if I change it with arrows or trying pick fonts from the list). Extremely frustrating experience – I have to work now with text in Photoshop or Affinity Designer first and then copy/export it to Illustrator. It slows my workflow around 5x with this. Horrible experience with the latest update!
P.S. Before anyone asks – all the font files are fine, I've checked them with FontBook app for any issues.