I made this very simple, so I could see what was happening:
Created a PatchScreen.
Added a Toggle to the Screen with a default value: runRoutine
On the OnCheck property:
Set(runRoutine, false);
On my main screen, created a button
On the OnSelect property:
Set(runRoutine, true)
I have a rectangle whose Visible property is set to runRoutine.
I click the button in the Developer Runtime mode.
The Pop Up appears very quickly and disappears, as expected.
On the Mobile Phone App and the Desktop Player App.
The Popup window appears but does not ever disappear, and it should.
The code is very simple. That's all there is to it.
It works correctly in the Developer Runtime, but not the others, unfortunately.