I just installed your plugin Woocommerce product slider free version to test it.
In my web site in developement, I have 6 products, with each 2 or 3 product categories.
I have set the slider the same way you described in others forum posts with
Hide out of stock items : No
Featured Product display : No
On Sale Product display : No
Catalog visibility : Shop and search results .
Impossible to show any product : "No Product to Slide", allthought the default slider works.
WP version is 4.9.6 (last one)
Woocommerce : 3.4.1 (last one)