WordPress themes and fonts reset

I edited my site’s layout and downloaded additional fonts.

I prepared a post, and using Classic Editor did my own CSS including the additional fonts that don’t come with WordPress.

It worked until a couple of days ago. I was in the middle of editing a post when my entire site reset back to default fonts, colors, etc.

I noticed that all my downloaded fonts deactivated and some even disappeared (typography). The fonts in my posts are overridden by the default ones (so for example, I want my post to have Times New Roman font, but it reverts back to default Georgia, and so on).

It looks like the whole site bugged out but I don’t see why.

I can’t revert back to what it was before that – I can revert it to the settings right after the bug, but not before.