I’m using Windows 10 v1909 but I’m guessing this solution should work in previous versions.
I too had the issue. First of all, your notifications must be set so that the “Windows host process (Rundll32)” notification has any chance of appearing (FYI, that’s the USB eject notification). So, at least temporarily make this setting: Settings -> Focus assist -> Get all notifications from your apps and contacts: (set to Off) (as opposed to having “Priority only” or “Alarms only” checked). Hopefully that’s enough make the notification start working. Also, for me, the notification was more consistent by using the task bar USB icon EJECT vs ejecting the USB stick from file explorer but, once it starts working smoothly again, either seems to work consistently. The notification is flakey so you may need to insert/remove a USB stick a couple of times before it starts working consistently.
If still not working, another setting that makes a difference is: Settings -> Ease of Access -> Display -> Show notifications for: (temporarily set to 1 minute). For whatever reason, this seems to help the OS notice the notification event whereas having this set to 5 seconds seems to have the effect of the OS not being aware that the notification event has occurred.
If that does not work for you then there’s one thing that happened to me that I don’t know how to solve, I had to do a restore to undo my mistake. When the notification popup occurs, if you hover the mouse over the popup, you see a settings gear icon in the popup (although I noticed on a locked down computer the setting gear wasn’t there). If you click on that settings gear then choose “Go to notifications settings” you will be taken to a settings screen titled: “Windows host process (Rundll32)” On that screen, I must have accidentally either set: Notifications (off) OR Show notification banners (unchecked). I could not find a way to get to that settings screen again to undo the accidental setting that I had made because the way to that screen was via the setting gear on the notification popup.
Last of all. If the popup is working consistently again, you can go back and change the “Show notifications for “ setting but, if setting it back to 5 seconds makes it flakey, set it to 7 seconds. If you want: Focus assist -> Priority only (checked) then you need to be able to add that notification “Windows host process (Rundll32)” to this list: Settings -> Focus assist -> Customize priority list -> Show notifications from the apps you add to the list below (there, you press: Add an app) and if “Windows host process (Rundll32)” does not show up in the pick list, then go back and make the setting previously mentioned: Show notifications for: (temporarily set to 1 minute) BECAUSE, for whatever reason, the “Windows host process (Rundll32)” will not show up in that pick list (and FYI nor will it show in the “Get notifications from these senders” list in “Notifications & actions”) unless the notification time is > 5 seconds. But, once “Windows host process (Rundll32)” has been added to the priority list, you can change the notification time to a lesser amount but as mentioned, using 5 seconds might make the notification flakey. What I noticed is that after a few successful notifications occur, it works consistently (even when using eject from file explorer).
