The New feature Clear All Slicers button (part of March 2023 release) works only for the 1st time in both desktop & Service. And it does nothing when you do some more slicer changes & try to use it 2...
Can you please try this on single select values? I think the issue seem to be with single select mandatory prompts. When you select something & use Clear All Slicer, it defaults to the 1st value in the drop down for the 1st time & it does nothing from 2nd time onwards.