This issue could be related to the fact that iPhones rely solely on mDNS for casting, while other devices may also accept Unicast answers. Therefore, it's possible that mDNS is blocked from the server to the iPhone.

To troubleshoot this issue, you can try the following:

  • Check the Wi-Fi network configuration to make sure that mDNS traffic is allowed from the server to the iPhone. Use Wireshark to analyze the network traffic and see if mDNS packets are being sent and received correctly.
  • Try casting from a different device to ensure that the issue is indeed related to the iPhone and not a broader problem with the casting system.