I do not find anything wrong with your setup. But try these and let me know what you get
In your level blueprint, before accessing the variable ‘W’ of your ‘Widget Reference’, do a validity check. ie Use an ‘Is Valid’ node and pass ‘Widget Reference’ as its parameter. Connect the rest of your network to the ‘Is Valid’ output. Attach a Print string node to the ‘Not Valid’ output. Now run it and tell us what you get.
I am trying to make sure your Widget Reference is actually pointing to an object that actually exist.