Mirrored display problem

Mouseposé 3.2.7 (direct download version, NOT Mac App Store) stopped working as soon as we mirrored the Mac’s display to our projector. The app is still running, but if we enable mouse clicks or the mousepose effect, nothing happens on the screen. This is a 27" iMac running 10.13.6.
If you need additional information, please let me know.

@Sixbillships Thank you for using Mouseposé and for reporting this problem. Can you please let me know if you’re using an eGPU to power the external screen?