As the many other questions that have been asked about this issue, here in this category, indicate...Notifications is down for some users and we don't know why. About the time some users started to ask about it being down, other users were still getting notifications on their YA page ( https://answers.yahoo.com/notifications ). I'm getting them myself.
Notification emails for the site have been down for many months, other than a brief period this past spring, and a brief moment last week (I got an email notice on 8/3 that one of my answers was reported, but nothing since then). I'm not sure if anyone is still receiving the email notifications or not.
No one here knows what the reason for the notifications being down is or when they'll be working again. Sorry. Just another glitch/issue we have to live with until it's fixed.