I can see several problems:
First, you should set the "recently viewed" option of the module to "no" as otherwise, it overrides the other settings to only display "recently viewed" products.
Second, you should set something in the "number of items" option of the module to tell the system how many products to display.
And finally, you should activate that option in the "modules under the product page" option of the HikaShop configuration, not the option "modules under the main area" as that second option is for something else.