Switching back to classic editor solved the problem here. Thanks!
In posts edited with the new Block Editor, some emails were getting through (tests and emails to the author of the post). Users who were subscribed to all the categories were also getting emails. But that defeats the purpose of subscribe2, because we want some users to only get emails from new articles in specific categories and not from other categories.
I just wish I had seen this thread 3 days ago. 🙂
