iOS 12 iMessage: Waiting for Activation (me.com vs. icloud.com)
I have a SIMless iPhone 5s that I updated to iOS 12 using one of my me.com Apple IDs. Key information: me.com Apple IDs have a fixed icloud.com alias, but the "true" Apple ID uses me.com.
iMessage is stuck on "waiting for activation".
The curious thing is that it can send messages. When it sends they use the icloud.com address. If I respond to the icloud.com address it's processed. However I can't send or receive using the me.com address. The me.com address does not appear as an option in iMessage settings, but it shows in the "reachable at" screen in Name, Phone Numbers, Email.
The "waiting for activation" bug is old, but I think the me.com/icloud.com bug is new with iOS 12.