I confirm (by marking "x" in the [ ] below: [x]):
Summary
When a Mattermost desktop app notifications comes through while Mattermost is in the background, no dot or notification is added to the Gnome notifications area (i.e. the pop-up when you click the date/time at the top of the screen).
Steps to reproduce
$ uname: Linux pop-os 4.15.0-20-generic #21-Ubuntu SMP Tue Apr 24 06:16:15 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux)4.0.14.0.0 (4.0.1)Expected behavior
There should be a dot next to the date/time and, when clicked, the notifications popup should have a notification.
Observed behavior
There is not dot nor notifications in the pop-up.

It seems the cause for this is that Mattermost is expiring or withdrawing its notifications, which cases them to disappear from GNOME Shell.
This is probably due to a mismatch in APIs between web notifications and GNOME notifications. On the web, withdrawing means it doesn't appear on screen. In GNOME, that means it won't appear in the notifications area any more (and there's no way to determine how long a notification displays on screen).
@cassidyjames By expiring/withdrawing, do you mean the notifications aren't persistent and disappear after a few seconds?
@jasonblais yes. Pre GNOME 3 (and I believe on some other platforms) this controlled how long the notification appeared on the screen. In GNOME 3, this controls how long the notification appears _in the notification area_ which catches notifications for later (much like the Notification Center on iOS/macOS, the notification dropdown on Android, etc.).
By Mattermost (or Electron, or whatever is controlling it here) telling the notifications to disappear, it is removing them from the notification area, making them much less useful than other messaging notifications.
@cassidyjames Makes sense. If we fixed this issue, it should also cover your report here? https://github.com/mattermost/desktop/issues/539
If so, I can migrate your report there so we have all the information part of the issue.
@jasonblais I'm unfamiliar with how Windows or macOS use notifications, but it looks like it might be the same issue.
@echosa @cassidyjames I've ported your issue description to the issue https://github.com/mattermost/desktop/issues/539
If it's not fixed with that issue, we can reopen this ticket.
Thanks for the follow-ups!
Most helpful comment
@echosa @cassidyjames I've ported your issue description to the issue https://github.com/mattermost/desktop/issues/539
If it's not fixed with that issue, we can reopen this ticket.
Thanks for the follow-ups!