Noto Serif disappeared while editing

I was in the middle of editing a post when my system fonts replaced Noto Serif. Other block editor styles changed as well; my line length, for example, got much longer. This is happening across browsers but only on this one site; I tested other WordPress sites that are still loading the correct editor styles. I tried deleting cookies, deactivating all plugins, switching to a default theme, and restarting, to no avail. Where did my block editor styles go? Did I change a setting I can’t find now? How can I get them back?