Pinterest no longer supports Buyable Pins
As of October 16th, Pinterest no longer supports Buyable Pins.
If you're using the Pinterest sales channel, then no action is required. Pinterest will convert your existing Buyable Pins into Product Pins. Product Pins link directly to the product page on your online store, making it easy for Pinterest users to checkout on Shopify. You can continue to sync your Shopify products to Pinterest through the sales channel, as these will now be discoverable through search on Pinterest as Product Pins.
Learn more about the Pinterest sales channel at the Shopify Help Center.