Filtering by category doesn’t work

Hello,
when I try to filter by product category I see the link generated looks like that “shop/?product-category=holidays” and it doesn’t filter anything at all. The category link really looks like “product-category/holidays/”
Moreover from your demo I see the link generated by your filter is https://demo.filtereverything.pro/product-cat-laptops/
So why does it behave differently on my side and puts category as a request parameter?