Hi Jack,
I changed your forum post to the Rhino.Inside - Revit forum Category.
You’ll want to see the guide on working with links if the project is using a different location.
Here i used the Query Links component to get the particular documents Categories and Queried that Document’s Elements by Category.
Hit the + by Zooming in (ZoomUI feature) to add the Document input.
Also note that some MEP Families are on Subcategories.