What settings did you change specifically? I am trying to set up a basic, single screen, 2 Player fighting game (something like Mortal Kombat), and I am facing the same issue. I can’t seem to find an example/tutorial of local, shared-screen multiplayer anywhere. Any information would be a giant help and greatly appreciated!
This is a really old post, but under Project Settings, Maps & Modes, Local Multiplayer, there’s a checkbox for “Use Splitscreen” that you will want to turn off.