Scrivener3.1.5.1 displays on my laptop but not on additional connected screen

My laptop is set up to display on a secondary monitor.
It does so perfectly on Scrivener but not Scrivener (it only shows on the laptop, but not the secondary screen).

Could you describe what that means? If you drag the project window over from your laptop display into the main display, it just vanishes?

Thanks for your reply. I have now managed to resolve the problem.