Issues with UserID Lookup Table Not Appearing in Query Editor

[Problem with Lookup Tables] I created a lookup table for mapping orgIDs with labels stored in a database. It works fine and I can query with the filter/breakdown "organization_lookup_name". Now, I created a second lookup table for mapping userIDs with labels stored in a database. I go with "Distinct ID" as we set it up with the app userID. Unfortunately, the attribute "user_lookup_persona" never shows up in my query editor. Any ideas? Does "Distinct ID" not work? I don't see any other property for user_ids..