As mention before - there is a notification cycle that happen every 10 minutes (by default) which sends on the notification area (the one you referring to) information about recently learned entities. The list includes the 5 categories you see in the screenshot
(domains, DCs, users, computers and groups).
If adding a user generated notification - this mean the mechanism is working as expected. Since the notifications only show "delta" (i.e. new entities) it is expected to only show you the 1 user.
Since the notification is active until midnight, it is possible it was generated in the initial cycle (after ~10 minutes from initial install) and was removed in midnight and you may miss it.
It will be interesting to hear from other people in the forum if they manage to see those initial notification or not. If this happen to other people (missing initial notification) we can investigate if there is a generic issue with the mechanism.
Hope this helps.
Microsoft ATA team.