[Shopify] Why aren't "Add to cart" buttons populated on my collection pages?

Without further customizations to your current theme, if you don't see the 'Add to Cart' buttons populated on each item on collection pages as follows:

Please note that our plugin implementation checks the following conditions to display the 'Add to Cart' button:

 

transformItems: function(items) {
  return items.map( item => ({
   ...item,
   _distinct: instant.distinct,
   can_order:
    item.inventory_management !== 'shopify' ||
    item.inventory_policy === 'continue' ||
    item.inventory_quantity > 0,
   queryID: item.__queryID,
   productPosition: item.__position,
   index: instant.search.mainIndex.getIndexName()
  }));
}

${!hit._distinct && html`
 <form id="algolia-add-to-cart-${hit.objectID}" style="display: none;" action="/cart/add" method="post" enctype="multipart/form-data">
  <input type="hidden" name="id" value="${hit.objectID}" />
  <p class="ais-hit--cart">
   ${hit.can_order ? html`
    <button type="submit" class="ais-hit--cart-button" data-form-id="algolia-add-to-cart-${hit.objectID}">
     ${ algolia.translations.addToCart }
    </button>`
   : html`
    <button class="ais-hit--cart-button ais-hit--cart-button__disabled" disabled>
     ${ algolia.translations.outOfStock }
    </button>`}
  </p>
 </form>
`}

Hence, you may review whether the products are in inventory and the 'distinct' option (Show products instead of variants) is disabled.