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.
This is 2nd time i have encountered this issue after 6 month. Previously it was in Objective-C project using AFNetworking and i used this solution and it worked on one go. Now same happened with Alamofire. Guys this solution is worked for me 2 times and i found this question is coming first in google so i am posting the answer.
Search in the workspace for AF_INET and change it to AF_INET6 anywhere you found. I think it must be inside the AFNetworking library or Alamofire library if you are using it. Its in the NetworkReachabilityManager class.
I found this answer from the below source.
https://stackoverflow.com/a/38196337/4030971
EDIT: - 24th June -
This helped me so many times but there is a strange solution to this problem also. In our recent project we have applied this solution but still apple rejected the application. Then we made a video which was showing that the app is running fine with connected to a NAT64 network created on a Mac from wifi sharing option. We appealed for review with the video and they approved the application. So if you are done with all your options, try this one too.