I hope you backup up your OpenLP data and restored it when going to an earlier version of OpenLP as they can interfere with each other and can cause more issues.
In terms of the display issues; I don't quite understand your setup, but it sounds like you might have mirrored your screen to the projector in the past, but now you are extending your screen? Extending your screen is recommended.
If you mirror your display, you will need to check "Display if a single screen" in the "Screens" section of the settings for anything to show.