We are adding Shopify as one of the destinations to our website. User can make product videos on our website and add to their Shopify store from our website.
If an error occurs during OAuth, the customer will see an error in their browser. On your end you'll be able to see that a user was redirected to Oauth and never returned.
If you haven't already, I recommend taking a look at our OAuth tutorial here. Setting up the example app should help give a better understanding of the overall flow.