IPv6 App Store Rejection

Question

Our update has been rejected twice today for ipv6 network connectivity issues. Our networking code has not changed between the previous release and this current release.

Answer 1

Please note that Supporting IPv6-only Networks and IPv6 and App Review link can be very helpful in determining what's the problem with apple rejections. In this specific case the articles clearly state that you can setup the DNS64/NAT64 test network but that "This test network is not exactly the same as the network used by App Review", that's why everything can work in the test environment and still have the app rejected.

Moreover:

The App Review network, like the networks deployed by service providers, does support IPv6-to-IPv6 connectivity. Thus, if your server supports IPv6, your app will talk to it directly, without going through the NAT64 translator. This is, in general, a good thing, but it can trip you up if your server claims to support IPv6 but that IPv6 support is broken. For example, if: the DNS name is incorrect the DNS is correct but the server is not listening on IPv6 the server is listening on IPv6 but fails when a request comes in over IPv6

So if your backend server has support for IPv6 the apple test network will use it, and it is what has been wrong in this case.

I add this as a reference and starting point for other users that experience the same problem