A couple things here for the Filter One Question by Another automation:
If you have NETs created in the data reduction for the _filter by_ question, they will be used to create variables in the new filtered question. However, if you have nets in the question to be filtered, variables for those are not created. You must recreate all the nets in the new filtered question.
The overall/main NET in the _filter by_ question does not have a variable created for it using the automation (just the sub-nets do). Sometimes people use this as their total row/column and rename it to something more custom and would like to create a variable for it using the automation as well. You can’t really do this if your _filter by_ question is a Pick One as the NET will be NA in the filtered question as the base is different for each category. You’d have to create some custom JS or R variable to do the NET calculation and merge it into the larger question.