Same here. For a while in 2018, I only got random notification, some late, some never. For the past weeks, I haven't received a single notification, even though there are several threads I subscribed.
I haven't been getting any since the website was given a going over - you probably need to reset your options, (I won't bother, as I regularly visit the forums anyway).
Sorry about that guys. I made some changes to our sendgrid SMTP account. I updated it in the forum, but I'm not sure if it fixed it. Could you please let me know if notifications are still not working?