Create NAT64 Network check box

Issue Reported by iTunesConnect:

"We discovered one or more bugs in your app when reviewed on iPad and iPhone running iOS 9.3.2 on Wi-Fi. An activity indicator displayed when attempting to login. This displayed for over a minute. Once it disappeared, no login occurred and the login screen still displayed. We've attached screenshot(s) for your reference. Next Steps Please run your app on a device to identify the issue(s), then revise and resubmit your app for review. Apps are reviewed on an IPv6 network. Please ensure that your app supports IPv6 networks, as IPv6 compatibility is required. For additional information about supporting IPv6 Networks, please refer to Supporting IPv6 DNS64/NAT64 Networks.

" I have tried the steps mentioned in the /discussion/https:/ <p style=

Could not able to get the 'Create NAT64 Network check box' as mentioned in the steps. no clue on how to resolve the issue.

The app is already on store and made few changes to the app on UI level, and trying to upload it and got the above message from store.

Please let me know if anyone has any solution to this problem, how to identify the issue and fix.