Probably Never Got Fully Made
From The Lost Media Wiki
If work was done on this episode, it was probably not made in full. The United States Copyright Office would not be a good source since it is also missing other episodes such as "Beauty and the Beach." The most accurate source on the episodes, (in my opinion) would be the Writer's Guild Associate. The WGA has writers listed for all sorts of lost shows, including some which have articles on this very wiki (like Teamo Supremo). The WGA has a list of every single episode that was officially released in English until Diamond Pearl, which does not include "Computer Warrior Porygon."