Hi!
Thank you very much for the details, I have found some issues with the configuration, and corrected them for you.
– On the General Options -> Sources panel, no post type was selected, so the plugin was not able to return anything, I have choosen the ‘Post’ post type for you: https://i.imgur.com/iHLPfbH.png
– On the Advanced Options -> Exclude results panel, there were included and excluded posts by categories selected, which were basically overriding the filter, I have emptied those as well: https://i.imgur.com/CcJbayL.png
I did it, because the filter alone should be enough in this case, no inclusions are required. The results will be limited to the selected category anyways. If you wish to exclude items that match the categories within the filter, as well as another category, then use the exclusion option only, otherwise it might not work.
I hope this helps!