Verifying Your Domain On Pinterest
To begin verifying the domain your using, you will at first need to ensure the store password is disabled, if your store is still not ready for launch you can re enable it after you are finished verifying your domain.
Please note this solution is only available if you are using a custom domain with your existing shopify store. You must also ensure that your root domain as your primary domain in the shopify admin panel.
A store using the basic .myshopify.com URL as a current domain will not be able to verify with a third party app.