Your template pages do not use Smootify's default URLs, /products/, /collections/ and /vendors/: set productsBase, collectionsBase and vendorsBase.
The symptom. Product pages work when you open them from Webflow, but the links Smootify writes, in the cart or in search results, open a 404 page.
Why. Smootify builds its links like Shopify: /products/<handle>, /collections/<handle>, /vendors/<vendor>. If your Products collection’s URL is product, as many 1.x sites have, the links point to pages that do not exist.
The fix. Add the URL of each template page to your options, in the head code before the Smootify loader:
<script>
window.SmootifyUserOptions = { productsBase: "product", collectionsBase: "collection", vendorsBase: "vendor" };
</script>Set only the ones whose URL differs, and add them to the options script you already have: a second one replaces the first.