iMessage issues iOS 17.3.1
iMessage issues on iPhone 12 Pro Max since updating to iOS 17.3.1. I can no longer send iMessage and it reverts to sending all messages via SMS - even with other iPhone users. I have tried to enable/disable iMessage, sign-out/sign-in iCloud, rebooted, and even restored the iPhone with an iCloud backup, turned-off contact verification, enabled/disabled airplane mode, verified the correct date/time, verified no iCloud outages, amongst other things. Nothing has corrected the problem. This occurs when on WiFi and the carrier's network.
iPhone 12 Pro Max, iOS 17