We’ve just tried it with the Storefront theme and it works fine!
If you want to use it in the Shop page, you should set it as follows (in YITH > Infinite Scrolling > Settings):
– Navigation Selector: .woocommerce-pagination
– Next Selector: .woocommerce-pagination a.next
– Item Selector: li.product
– Content Selector: ul.products
Please try this solution and let us know if everything works fine!