I've somehow disabled touch from affecting UI in my project?

I’ve ran into a weird problem. At some point all ui buttons stopped reacting to touches.

I’ve narrowed it down to being a problem with some project setting or something by creating an empty scene with gamemode overridden to defaults and only adding a button widget which simply prints out hello to viewport in level blueprint. There should be no other blueprints or code from my project in the test level, only UE default empty PlayerController, Pawn etc.

Any ideas what could be causing buttons to not react to touch if only some settings have been changed?

Is there any way to debug this? See what is happening when there is a touch event and why the button is not responding to it?