In order to work with Shopify, at the Admin API level, you have to set the privacy settings of your App, where you promise to not mess around with customer info should they grant you permission to see it. So for a custom App, not in App store, just fill it all out and ask for permission to see customer info. You get it. For a public App, they review your request, so you have to wait.
In your Partner account, for the App, under API keys, you'll find the links to privacy settings.