Remember to add an EventSystem to your canvas.
Hierarchy → RightClick on canvas → Create → UI → EventSystem.
Then check the inspector for the new EventSystem, and there should be a red error telling you to update to the new input System. Accept that.
** your mouse still won’t be able to click the buttons when you press esc. - that will be fixed in the next lesson.
hope that helps, It gave me a headache until I figured it out.