I have loaded your gui file in the editor, and I found out that your button, is.. well.. not a button :-), its a label gadget which is why it cannot be checked with alphagetactive$(). Make the "button" a button gadget instead of a label gadget, using the dropdown gadget to the right in the editor. The default selected gadget type in the editor is a label gadget, which is only useful for displaying static stuff, ie no interactive gadgets.
Hope this solves it :-)
Hope this solves it :-)