Q: Cannot login into iMessage

Hard to believe that this post originated in 2013 and that there are still people, myself included, still experiencing this intolerable annoyance in 2016!.. with no definitive or satisfactory solution in sight. Having tried most if not all the 'solutions' in these posts I've ultimately had to discontinue my use of messages app altogether... 'It just works'?.. 'It just won't!!! :/

This problem just happened to me recently (July 2016). I've been using my one Messages account on an iPhone, iPad Pro, and mid-2011 Mac Mini. Recently it stopped working on the Mac Mini (still works fine on the other two devices). Deleting com.apple.ids.service.com.apple.madrid.plist makes no difference. On the Mac Mini, I try to log in to the same ID that is working successfully on the iPhone and iPad, but on the Mini it says "Could not sign in to iMessage. An error occurred during activation. Try again." I can log in to iCloud from the same Mini, this problem seems to only be affecting the Messages application. I'm surprised to see that this has been an issue for so long... Very frustrating.

I'm running 10.11.6, and have tried just about everything suggested in this thread. I also just realized that FaceTime no longer works, as well. I'm able to use them on the other devices, and this same Apple ID works fine elsewhere on this computer, in iTunes and App Store.

You might want to consider starting a new discussion. Since this one is a couple of years old, less people are likely to look at it. A new post would be much more visible. You can link to this one. Post in El Capitan.

Hi,

If you have the Serial Number showing on your computer and you have tried and Safe Boot and a NVRAM reset AND tested in another Mac user account on your Mac then you should phone Apple Support (Apple Care)

This can be long and tedious but it is the only way to reset the account.

Basically the App not only uses the Apple ID and Password to login but the Serial Number as well to prove it is "you".

There is no reset on the App so you have to call.

Level 1 responders and Script led and are trying to solve Apple Care issues.

You have an Apple ID issue (free to fix)  and do not need to do all the tests they suggest.

Politely ask to speak to someone higher.

Level 2s may or may not know about the issue (judging by what other people have posted back).

Again they may want to run test with you and gather data (Apple know there is an issue but cannot find what is triggering it).

Updating, Upgrading and Reinstalling do not work as the issue is at the iMessage Server end.

Ask the Level 2 (or Higher) to look at the sever and check.

At this point they may involve the Engineers as it now seems they are the only ones allowed to reset the server.

You may get a messages that it will take 24 hours (or upto to 5 days) to reset.

9:17 pm      Monday; July 25, 2016

As of a couple of days ago, I started having this problem only on my MacBook Pro. One minute it was working and the next it simply stopped. I have it a couple of days, was on and off my MBP and by the third day when it was no longer updating my conversations from my iPhone, I started to trouble-shoot. Of course, I googled the error messages and it gave me some quick workaround fixes that did not correct the problem. I tried for over two hours, restarting my MBP, signing in/out of iCloud, updating the timezone, and still had nothing. Finally broke down and called Apple support. Within seconds, a tech called me back I told him of the issues and he tried to walk me through some fixes, which turned out to be the same from when I Googled the problem.  After about 45 minutes he requested if I was comfortable with having the problem escalated which meant divulging my iCloud password information and security questions answers, which I confirmed to do in efforts to help provide answers and a fix. I was told it would take about four days but the tech would follow up with me the following day to advise what was going on. In less than 12 hours, he called me back and said the problem had been resolved and I could try logging in again on my MPB to iMessage (and FaceTime).  Before I did that, I restarted my MBP, just in case, and after bout 2 clicks of the log-ing button, iMessage was back online, however it has not updated any conversations from iCloud (even after 3 hours of waiting for iCloud to push info to me), but I am at least happy the situation was resolved.  No real communication as to what the problem is, but I suspect a bug with communication. Hope you get some fixes yourself.

Hi,

...

iMessage was back online, however it has not updated any conversations from iCloud (even after 3 hours of waiting for iCloud to push info to me) ...

Unfortunately it will not.

During the time your Mac or iPhone is unconnected to the iMessages server or Not allowed to receive iMessages it is effectively de-registered.

On an iPhone this can be if it is in Airplane Mode for too long (days)

Or the iPhone number becomes unticked in Settings > Send and Receive (it should not but it is not unheard of).

Or just long term lack of Carrier service or Wifi.

On the Mac you can also of course Sign Out.

You get the situation that is the main reason behind this thread in the fact the Server decides it does not like the iMessages Login from your Mac.

The iMessages Server will only send iMessages to those devices deemed to accept iMessages at the time.

Once delivered to all devices then they are deleted from the Server.

7:56 pm      Wednesday; August 3, 2016

for the    Points

8:15 pm      Tuesday; September 6, 2016