Disconnecting a monitor would not help, but reconnecting a missing one might.
This is what you could try unless the SketchUp support has a better suggestion:
Start the geolocation
type Alt+Space
type m (or, if your Windows is not in English, the letter Windows uses as the shortcut for Move)
Type one of the Arrow keys
Move your mouse around. You should see the window appear. Place it where it is visible and click.