Lets do this. If you are noticing that there are only certin people that you cannot iMessage the issue might be indeed with the service itself. Remeber iMessage is still a work in progress as is other apps such as Maps, and Siri. Because of this it is usually never a device issue rather a software/service issue. Looks like you have done a very good job with troubleshooting. If you have already contacted Apple what might help is getting you to a Senior Advisor. I cannot promise results but after doing some basic troublshooting they can go to engineering and see if there is any resloution at hand or if this is just a iMessage error and we will just have to hang tight while they try to reslove it. Again im NOT promising you anything but this is worth a try.
Hope this helps out a little!
Same here, can not login to iMessages, I've reset password, re-confirmed itunes account etc.. but always get this message:
Could not sign in to iMessage.
The server encountered an error processing registration. Please try again later.
This has been the case for about a week. No iMessages for ages, impossible to share images etc.. iPhone only accepting Text Message, MBP & iPad not recieving anything either.
I had sent several messages to a variety of people and then I started getting calls as to why I was not answering their texts. I told them I had and I sent them a screen shot where I had responded, but they said they never got them. After further investigation, I noticed at the top of the screen it said sending 1 of 5 and the texts were a dark blue color and none of them had been delivered. I clicked on the text and sent it as a text message instead of an iMessage and it went through. Very frustrating!