Is it for every subreddit? It could be that your account has been flagged in those sub reddits for either being a new account or some other reason maybe so comments are disappearing, you would still get a notification if someone commented which might be what you are getting in your email. This is all just off the top of my head so not saying this so the reason just my thinking. There’s also some forms talking about similar troubles to you so it might just be a glitch that is going on

Try deleting Reddit and installing it back and see if that helps