What determines which screen the account control popup will appear on?

I'm running a Windows 10 system with one touch screen, one normal screen and no mouse or keyboard. I need to run an application with administrator privileges.

I'm worried about which screen the Account Control popup will appear on - if it appears on the non-touch screen then users will have no way to allow the program to run.

I know that:

It runs on screen 2 on my development PC (with mouse and keyboard, no touch screen), regardless of whether screen 2 is on the left or right
It runs on the same screen regardless of whether the application was launched by a shortcut on the left or right screen.

I tried to google this, but the only things that came back were links on how to disable User Account Control, which we really don't want to do.

What is the logic that determines which screen the popup appears on?

[Edit for new things I have tried]

Unplugging screen 2, running the application, closing the application, plug screen 2 back in.
Dragging the UAC popup to screen 1, clicking details, changing UAC settings and returning them to the original state.

[SOLVED] I figured it out (at least partially) but I can't mark it as answered for at least two days.

Basically, after unplugging and replugging screens the other way around, changing the primary display worked. This didn't work until after I did the plug/unplug, but there's no guarantee that was the thing that did it, since I'd tried a few other things.

Solution

So after physically unplugging and replugging monitors so that screen one became screen 2 and the reverse, switching which screen was the primary display works to control the popup now.

Changing the primary display didn't work before. But it does now. I have no idea why - there's no guarantee that it was to do with switching them around.