Using already existing improvement (Chateau) but it is invisible.

[traydenpoke]

Hello, I am using the Chateau improvement from France to create a custom civilization. I have it functioning as intended except that it shows as invisible. I have tried modifying the ArtDef files and including Improvement.artdef and Landmarks.artdef, modifying IMPROVEMENT_CHATEAU to my unique improvement, but nothing seems to work. I was able to fix the same problem with a unique district for another civilization by just changing DISTRICT_INDUSTRIAL_ZONE to the name of my unique district, so I am wondering why it is not working. Thanks.