FB dark mode not working

[Gary02468]

I used to have Dark Mode working in my S21 Ultra Facebook app (currently version 351.0.0.38.117), but now it's not working. I can get to the Dark Mode option in the FB settings, but when I tap it, it does not bring up the toggle buttons; instead, the Dark Mode line briefly highlights, but nothing else happens.

Does anyone else have this problem or know how to fix it? I can force dark mode in the phone's Developer Settings, but that will apply to all apps and I have some that don't handle it properly, so I don't want to do that.