Edit: Fixed, if the same happens to you check the comments.
I cross checked some pages with two browsers, only one of them logged in, and I couldn’t see all posts when logged in. And though I can still open them through the URL, I can’t see any comments on the posts that don’t show up.
Same happened on an iOS app, so it’s not a browser issue.
Ok I fixed this pretty quickly, but the issue was I that I could only see posts in “Undetermined” language. I fixed it by going to my account settings, selecting English under Languages and pressing save. I guess I accidentally did the same thing earlier and deselected it instead.