Ok so at 16:10 in my Video Tutorial i create the WidgetPopup variable. I set this variables type the same as my Widget itself. I noticed your widgetPOPUP variable type is not the same as your Widget that you created. You have 2 options, change your variable type to the same type that is your Widget or use a CastTo node to cast to the same type as your Widget before you attempt to use the widgetPOPUP variable to setup the Bind node.
Since your variable type isnt the same, your Event Dispatcher is “out of scope”, this is why you cant Bind to it correctly.