Hide values in slicer

I found a post which shows how to hide values in a slicer, and this was working fine for me. (Using a different visual, select the values you want to show, and then convert back to slicer). In the last couple of days, this doesn't seem to be working though.

I have selected the values I want to show on my slicer, and then converted the visual back to a slicer, but it keeps reverting back to show all values, and not just the ones I selected. Any ideas why?

Values I want to showAll values appear when I revert back to slicer