Re-tried the app install via testflight, checked my company firewall, verified accessible via data sim card.
Notably absent from that list is MacNAT64. Have you tried that?
You can learn more about this in my Supporting IPv6-only Networks pinned post.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"
Seems like you are right. I will try that. Thank you.