Trying to apply a Category Filter to derived Question

I am using SQL to generate a custom question that I want to use as the foundation for further questions. In my query, I have a ‘Language’ and a ‘Partner’ category filter on String fields with the same names.

I am creating an aggregation question that counts some entries and sums the totals of another field. What I am trying to do is filter by the Partner and Language so that only some values are used to generate the calculations.

However, in my Dashboard I am unable to apply any Category filter because it reports there are no valid fields.

Try redefining the field in the originating table (admin panel>data model>schema>table>field>rightmost drop down) as Category.

I changed the metadata type of both of those underlying database fields to Category and it did not appear to help.

I ended up having to create a scratch native query to get the filter to work, instead of being able to apply a filter to a Question built off a saved one.