Power BI Visual and slicer relationship error

You can learn about Power Bi relationships here

https://learn.microsoft.com/en-us/power-bi/transform-model/desktop-create-and-manage-relationships

Your Job Assignment table has an One-To-Many relationships with Single cross filter direction.

 Therefore slicers on Equipment wont apply to Sites or vice versa.

Consider using Power Query to merge the Equipment and Sites to give you a single table.

This is not necessary the best practice but will give you very quick results if you are a Power Bi novice

https://learn.microsoft.com/en-us/power-query/merge-queries-overview

Or build a start schema with who, where, what, wher and when dimensions and fact table for measures.

Unfotunatley you have provided insufficient information for me to design a star schema for you.

However you can learn about start schema modelling here. 

https://learn.microsoft.com/en-us/power-bi/guidance/star-schema

Please click the thumbs up button for the ideas.

Also click [accept solution] if any work.

Thanks