1.5.1 mouse doesn't work in project imported from 1.1.3

I'm trying to use mouse functionality in a 1.5.1 game with no results. All games I create from scratch in 1.5.1 work fine, but this one project that I've transferred over from 1.1.3 just doesn't seem to accept mouse input.

The mouse pointer is visible on the screen, but mouse commands just don't generate their callback and mouse behaviours don't work.

In my common/preferences/defaultPrefs.cs I've got

$pref::Input::MouseEnabled = 1;

Is there any other place where mouse input might be getting disabled due to old 1.1.3 code?

Here's my game.cs startgame function:

function startGame(%level)
{
	exec("./background.cs");
	exec("./player.cs");
	etc... about 10 more files that don't get loaded in this test

   Canvas.setContent(mainScreenGui);
   Canvas.setCursor(DefaultCursor);
   
   new ActionMap(moveMap);   
   moveMap.push();
   
   $enableDirectInput = true;
   activateDirectInput();
   enableJoystick();
	
sceneWindow2D.loadLevel(%level);
}

I'm just trying an empty level with 1 object and a generic mouse button behaviour and nothing happens.