I have a student that can only see the discussion posts of a few of his peers, not all of them. It's the same few people each week. He can also message only those students via Canvas, no one else in the class. Any idea how to fix this?
I would guess that the option to limit interaction with section members only is the issue here. Sometimes that option is enabled for enrollments to meet regulations (like FERPA in the U.S.). Depending on permission settings on your Canvas instance, you may be able to change the setting yourself or you may need to contact someone from your eLearning, IT Department, or similar to change the setting if that's allowed under school policies.
Interesting, I was pretty sure I had hit the nail on the head, but apparently not. Are there multiple sections in this course or just one? Also wondering if there is only one student with this issue for sure, or maybe this student and the other few he/she can see have something in common. I'd say this is going to be a hard one to troubleshoot in the community. Have you reached out to local Canvas support at your school?