Looks like the IPV6 was not the issue at all, I don't know why they keep saying that the app crashed using ipv6 network. once my app doesn't even connect to the internet, so I asked them what they did to produce that error "Your app crashed on iPad or iPhone running iOS 11.2.5 connected to an IPv6 network during our review." and they answered me with this:
"We noticed that several screens of your app were crowded or laid out in a way that made it difficult to use your app.
Please see attached screenshots for details. These screenshots represent some examples of this problem but may not represent all instances of this issue.
To resolve this issue, please revise your app to ensure that the content and controls on the screen are easy to read and interact with.
For more information, please review the following resources on the iOS Developer Center page:
- UI Do's and Don'ts
- iOS Human Interface Guidelines
Please make any changes you see needed to bring this app into compliance with the App Review Guidelines, then resubmit for review. Once this issue has been resolved, we can continue with the review of your app.
App Store Review"