Hey @eric ,
Welcome to the community! Feel free to Introduce yourself 
to the community if you want to! 
I suggest you check out our Power BI playlist:
https://youtube.com/playlist?list=PLlI5Dyt2HaEsZHG2WJ75WIM0Brx6VHT2S&si=e4Gktr43vPoyoMeE
You are not seeing the category field because what you selected is a Mesh object, not a Revit element.