I've noticed when I use SkyRoof on my laptop with dual monitors, the program doesn't seem to switch back to the primary display when I next run it on a single monitor.
I sometimes run the program on my second monitor when the laptop is at my desk. Then I'll use it outside, only with the laptop screen. The program is loaded (and shows up on the task bar), but you can't see it on the screen. When I plug in a second monitor, it pops up just fine. You can't seem to move it to the primary display when you have only one screen.
I'm using Windows 10 on a Lenovo laptop.