When working in Presenter by Worship Extreme, you may run into an issue where Presenter shows a red "Main Display Off" message in the upper right corner, even though the On toggle is checked (reference the image below).
This discrepancy is because there are two layers of on and off settings in Presenter that control your external screens. The On/Off toggles in the picture above control whether your presentation is being projected to the screens or not. But the presentation can't be projected if the external screens are not set up properly first. Think of it this way: a TV needs to be connected to a power outlet in order for you to turn it on or off with a remote. Similarly, Presenter needs to be properly routed to an external outlet (i.e. a projector, TV, monitor, etc.) in order for you to be able to toggle the presentation on or off with the above buttons.
Navigate to Presenter's Screen Configuration settings by clicking the display-shaped icon in the upper right corner and then ⚙ Configure. Alternatively, you can click the ⚙ gear icon > Settings > Screen Configuration to arrive at the same place.
There, you want to make sure that your screen(s), left, are routing to the correct Display, right, and not set to Off. The most common setup is to have Main Audience Display routing to Display 1. Make sure to click Save if you make any changes here. Once this is completed, you shouldn't have to touch these settings very often, and your screens should now be showing your presentation. If you don't see any Display options, then you'll want to make sure that your cables are good and that all your computer(s) and screen(s) are hooked up properly.
Once your screens are routed properly per the program settings above, you can use the On and Off toggles under the display-shaped icon in the top right corner to turn your projection on or off on the go. For example, you may want to toggle the presentation off while you're editing the service and then toggle it back on when service begins. Remember, the toggle buttons don't turn off the screen itself, but rather just turn on/off the presentation from being projected to the screens.