Students not getting notifications for pull request feedback

I have multiple classes on Github Classroom, and when I make an assignment (with the Feedback Pull Request option checked), one class will get email notifications, and the other won’t. I checked account their settings > notifications (between the two cohorts), and they’re identical (the box is checked for pull request notifications). They get an email when they accept the assignment and it tells them they have access. But they don’t get a notification when I give them a comment via the feedback pull request (nor the initial email telling them about the feedback pull request thread).

Any ideas? Thanks in advance.

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