To reproduce:
1. Open users attached project "NetworkExample.zip"
2. Make sure that in Services tab Multiplayer is set up
3. Build for iOS
4. Open Xcode project and deploy to iOS device
5. On Editor enter Play mode and press "Create Room" button
6. On iOS device press "Join first found match"
7. Observe as "Connection Established: True"
8. Set up an ipv6 connection on MacOS by following this: https://developer.apple.com/library/archive/documentation/NetworkingInternetWeb/Conceptual/NetworkingOverview/UnderstandingandPreparingfortheIPv6Transition/UnderstandingandPreparingfortheIPv6Transition.html#//apple_ref/doc/uid/TP40010220-CH213-SW16
9. On iOS device connect to the Wifi that was set up in step 7
10. Repeat steps 4 and 5
11. Observe as "Connection Established: False"

Expected result: using an ipv6 connection type connection is established between devices
Actual result: using an ipv6 connection type connection between devices can't be established

Reproduced on:
2018.2.19f1 2018.3.0f1 2019.1.0a11

On 2017.4.17f1 pressing any button on an iOS device does nothing.

Device reproduced on:
iPhone 6 Plus iOS 12.0.1
iPhone XS Max iOS 12.0

Notes:
Reproduced on .Net 3.5 and 4.x