You just have a visibility or a z-order problem. These are settings displayed on each of the widgets you add in your ‘Designer’ tab.
z-order is the layering order of your widgets. The higher the more on top it is (if I remember correctly).
Widgets are layered using this order + the order at which you put them in your widget hierarchy (which means inside the z-order 0, the widgets which is on top is the widget at the bottom of the widget hierarchy you created).
If you create several widgets with the same z-order on top of each other from different places in your code, the latest created will be on top of the others.
Visibility has different settings:
Hidden - can not consume mouse clicks, is not rendered on screen, does not calculate tick and anims
Collapsed - same than above but removes the room it takes up in the widget as well
Self Hit Test Invisible - this widget will not respond to click events
Hit Test Invisible - this widget and all widgets attached to it will not respond to click events
Visible - everything works!
To me you just have a z-order problem: something invisible / with 0 opacity is in front of your button and is preventing your mouse to detect it.
Simply remove everything but your button and see if it works.
If it doesn’t, it means you have a visibility setting issue: something is not setup properly (check out your visibility settings and see if it makes sense according to the description I gave you).
If you want more details, quote me with my name (it will generate a notification for me).