Slicers not affecting certain tables?

let's clarify; we're in Desktop forum so we're discussing a report - rather than a dashboard I will presume since dashboards are in Service.

You have a slicer on the same page as another visual - and when selecting values in the slicer, the visual is not changing?  that is my interpretation of your post.

I would delete the slicer, and re-add it as a quick sanity check; but assuming the behavior is the same it means the data set in the visual is not being affected by the filtering of the slicer even though you say the tables are related.  A guess is the impact/result of another table's join is the reason. 

Rather than use a separate table for the slicer content - can you use the field of the dataset in the visual directly as your slicer source.  Sometimes this is possible depending on the data structure.

Another thing you could do is make a copy of your pbix - and delete the joins of those other tables and experiment that way.  This would free up the impact and verify that it works in a simpler set up.  Not the final answer of course but possibly the path to understanding.