Mac: I keep getting a black screen when I try to play

My main computer screen just goes black when I start the app, or enable a second display.

*Depending on your macOS, pictures may not represent the current model of System Settings. 

Solution: 

Go to System Preferences > Mission Control

Make sure that "Displays have separate Spaces" is checked. If you change it you will need to log out and back in for it to have an effect. 

Restart Sidekick and everything should work!