Link Slicers From Multiple Data Model Tables

I am trying to link both of my pivot tables to my slicers, so that they both change when one slicer is edited. I know this is possible as I've seen many solutions online for how to do this, but it does not work for my case, and I am wondering why. See attached spreadsheet, tab "Summary." I've created relations between my two tables by a column called "Identifier," and then I reported the connections for the two tables in the slicer settings. However, when I change the slicer, it only changes the first pivot table.

Your pivot tables aren't using the same fields. The Site field in one table is not the same as the Site field in the other, so a slicer attached to one will not affect the other.

It would, but filters work from the 1 side of the relationship to the many, not vice versa, and your relationships don't map properly.