Quantity box dissapear

Hello,

We suspect that your custom isn't the root issue, first test you can do is try with a default template to see if your quantity input
still not showing, then there are good chance that your issue is misconfiguration, go to Component => HikaShop => Configuration.
And in Product Options part, check this settings :

Hi,

The issue on your website is that the product page was customized and the quantity input field was forcefully hidden.
So either this was done on your end in the past, or this was done by your template provider for some reason.
So that's something you're supposed to deal with on your end or with your template provider.
Now, you should be able to restore the quantity input field by adding a bit of extra CSS on your website:

.hikashop_product_page .hikashop_quantity_form div {
    display: block !important;
}