Output parameters are not going to work properly from a popup view as the popup is not actually within your base view.
See here: How do I use the Input, Output, Input/Output options on perspective's view params? - #3 by cmallonee
So, if you're expecting a value on your base view to update based on a parameter in your popup automatically, put simply, it will not.
I tend to use messaging to pass data back from my popup views, but as is pointed out in the above topic you can use session properties as well.