Cannot turn off font filtering

I cannot turn off font filtering in InDesign. It's somehow set to "sans serif" and when I try to choose All Classes, it does not accept that selection, and I cannot use most of my fonts. Even if I type in the font I want, it does not show up, as it is permanently set to Sans Serif. How can I fix this? Not sure if it's corrupt, but I've done the usual - restarting, updating the app, etc. Thank you