We’re trying to provide a way for our customers to authorize us to connect to their Shopify account, and import payment data into their account in our system. Do we have to create an App in the App Store for this? They will not be initiating the connection from Shopify or the Shopify App Store, so I’m hesitant to go that route. Isn’t there a way for them to just go through a regular oAuth path and allow us to connect to their store to pull information? We tried this but the Install App button is always grayed out somehow.
You will need to make an app to get the api access.
If it’s just for one store then you could make a private app which does not need to be on the app store etc
If you need to use it for multiple stores then you likely should make a public app.
App types · Shopify Help Center
If you are doing it to fetch customer data then keep in mind the ‘protected customer data’ protocols Protected customer data (shopify.dev)
What about just having the customer create a custom app in their shop, and provide the admin api key for connection?
Yes if its just a single client then you can just create a private app on the store.
What about the custom app route I described above?
Hi @busupport 
I’d recommend reviewing this guide on how to use access tokens for custom apps in the Shopify admin. This help doc outlines the steps for revealing the access token via the API credentials page as well.
Hope that helps!