IAP: BuyProductID: FAIL. Not initialized In-App Purchases error

>error "BuyProductID: FAIL. Not initialized"

This error message is not an iOS error message. Are you using someone's IAP code in your app? If so, ask them.

Might be better to post in unity's IAP forum h ttps://forum.unity.com/forums/unity-iap.112/, rather than risk being off-topic here in devForums.

We use Unity3D. The thing is that the same app works sometimes and sometimes do not. As far as I know, we do not use any server besides the Apple IAP service. So if the same code sometimes works and sometimes do not and the only thing that can be different is related to Apple. I think the issue is Apple related, so that's why I'm asking here. Don't you think? Thanks for your answer!

As I said it worked a short time after adding bank details and taxes form on Apple. Then it stopped working after one day and no changes. Apple reviewevers says it's something about the code, but the code has not changed... Why it was working during some time then stopped if the code is the same?

>but the code has not changed...

Might be a mistake on their end - did you appeal? How many times? What did you/they say?

Something in the code you are using, most likely from Unity code, is generating this error message. You need to figure out why Unity's, or your code would generate this error message. It is possible that Apple is causing Unity to generate this error message because of an issue your app is having interfacing with Apple's IAP system. But you have no reason to presuppose that. And 'not initialized' coming from Unity code suggests something is wrong with the way you have implemented Unity's code, doesn't it?