TestFlight and IAP question

Depends what you mean by "release". The app does not need to be released to the App Store for the public but as TestFlight handles the distribution, it build would need to be submitted and it will be made available to those you invite internally or externally. note: If you use with external testers, the app will need to be approved. See this doc for more info: https://help.apple.com/app-store-connect/#/devdc42b26b8

Another option distribute directly via Xcode and test against the sandbox environment. This will use the in-app purchase products you have configured in App Store Connect. https://developer.apple.com/documentation/storekit/in-app_purchase/testing_in-app_purchases_with_sandbox

Thank you for the reply, by trial and error i figured out what was wrong a few hours ago. So i'll post here to make sure other people might get some help.

To get the in app purchases working,

• You do not need to have an app published already, just a testflight app is enough, however if you are adding IAP to your already on TestFlight project, you need to upload it as a new version and get it reviewed again.
• You need your IAP in the App Store Connect, at the "Ready to Submit" status.
• After you get your IAP's "Ready to Submit" status, In App Store Connect's "Agreements, Tax and Banking" you have to get the "Paid App" agreement in "Active" status otherwise you get "UnityIAP:Received 0 products" error. (Which was my problem, i wish there was a popup or something that said, "Hey, you added this IAP but for it to work, you need to agree to the Paid Apps agreement!" This would have saved me hours.)

Apple is not so clear on what steps you need to take to get things rolling, you have to stumble upon them by yourself, or at least that was my experience for the past few hours. Hopefully this will help some people save some time.