If the game defaults to the incorrect monitor, Simply do the following
1, go into Settings, Display and change Display Mode to “windowed”
2, Click Apply, then click YES
3, Drag the game over to the correct screen by left click and holding on the bar at the top of the game. Drag the game to the TOP of the correct monitor
4, Then going back into Settings, Display and change Display Mode back to your desired mode, i.e. Boarderless of Fullscreen.
5, Click Apply, then click YES
Problem should now me resolved.