For a button to work properly:
– A button that is a child of a canvas object
– The canvas object must have a GraphicRaycaster component
– There must be an EventSystem object somewhere in your hierarchy.
– If you messed around with the InputManager be sure you still have the submit input (and it does not give errors on run)
Unity will build all this automatically if you create your button from the GameObject menu. But not if you add a button component manually.