Moodle 3.5.6+ (Build: 20190514)
We use forums as a regular activity in our courses. Until this week, that seemed to be working very well. But all of a sudden, students cannot reply to forum posts. Not in simple discussion forums. Not in standard forums. They can start new topics in a standard forum but cannot reply to existing ones.
We don't use groups at all. I double-checked the forums to make sure they were set to no groups.
The forums are set to "do not lock discussions".
The time period is set to "don't block".
Students have both reply to posts and reply to locked discussions permission. I verified by checking permissions in the forum for multiple students.
Date and time is correct on the server.
Courses are all in weekly format.
I tried searching in tracker but didn't see any issues there related to this. Or at least I couldn't find one.
Has anyone seen this before? Any ideas what might cause it?