Hi and welcome to the forum
Yeah, I just tried it, no pop-up windows seems to show up. However, the reminder shows up in the Cortana windows on the Start Menu (the Metro Tiles), and it also shows up as a blip on the Notification Menu on the lower-right task bar to the right of the System Clock. When you click the
"NOTIFICATIONS", you'll see it listed at the top. And the little icon shows a "1" in there. Certainly not what you are used to with older pre-W10 apps. You can use MS Outlook (versions 2003-2016) to provide that pop-up Windows (that costs money unless you have a copy laying around in a drawer somewhere. Alternatively, you could use the free Google Calendar to set reminders via one of your browsers (Edge...