products not showing from Category

Hello,

Not sure that my answer will be enough to achieve your needs, but I think the simplest is this set of settings:
1. Define your product without price
2. Allow the free product to have a button.
in HikaShop Configuration => Main tab => Product part

3. Then process an override in your language file (If this is relevant to your product page display)
=> Learn here how to process a language override.
FREE_PRICE="Free" for FREE_PRICE="Quote request"
OR
For your add to cart button :
ADD_TO_CART="Add to cart" for ADD_TO_CART="Quote request"

Hope this can help you
Regards