i did buy premium but i have problem 404 pages subdomain and product pages

Work for product_tag?

I have enabled the subdomains option in our host as below https://www.siteground.com/kb/how_to_enable_wildcard_subdomains/

And enabled one of our product category. But the url is loading the homepage of our site.
eg: productcategoryslug.domainname.com

when adding to the cart the button works as normal but the product does not add to the cart when clicking the modal.

I want to get this right before I push it live but I think it will not work on a staging site. Can I? what do I need to change to do it ?