- your store URL;
- page URL with the issue you mention;
- storefront password (if your store has one).
Have you installed any apps or hired developers?
Your "add to cart"'s form is simply gone. This is a very serious bug.
I'd highly suggest that you install a fresh copy of the Debut's theme instead, there may be other grave bugs around your website that you didn't notice. Start fresh and download a new copy.