iMessage stopped working on High Sierra

Hi,

Test first

On you Mac version set the Apple ID as the only active ID being used.

(The Send From drop down will disappear)

On the iPhone set the iPhone Number as the only active Send and receive item (NO need to Log out/Sign Out of the Apple ID just make it inactive)

Now on the Mac version start a New Message and manually type the iPhone Number into the "To" spot (as it will not call up the My Card from Contacts).

Now send the iMessage.

If the iPhone does not get it then the Mac Version is not logged in.

If that is the case do the tests and suggestions in this User Tip When the iMessages account will not Login

It may turn out to be the server end so you may need the last bit about Phoning Apple Support.

This can be long winded and slow as you move up the responders until someone can actually check the server and see if your Mac's uses of the Apple ID is blocked on the iMessage servers.
The Serial Number makes it Device Specific.

The app servers make it App Specific as well.

The ID may therefore work on other devices and other apps.

9:59 pm Wednesday; November 15, 2017

Hi,

From Yosemite onwards various people have had issues with the Messages App not being able to log back into the iMessages Server after either an Update of an Upgrade.

AS I detailed above testing is the first step by isolating the Mac and the iPhone to their relevant IDs then seeing if you can iMessages from the Apple ID (Mac) to the iPhone Number.

IF that "proves" that the Mac is not logged in then you need the link.

9:09 pm Tuesday; November 28, 2017

Hi,

Are you saying that if you type your iPhone's number in to the "to" spot including the Country Code that it identifies that as you ?

My experience is that using your own iPhone Number or Apple ID will not bring up the My Card info.

9:27 pm Tuesday; November 28, 2017

And ?

What was the outcome of doing that ?

7:55 pm Wednesday; November 29, 2017

Hi,

iMessages is not an iCloud App (yet) So singing in and out of iCloud will do nothing.

Signing In and Out of iMessages on the Mac might help.

(you could in fact use a second iCloud valid Apple ID instead of your iCloud one)

Test iMessages by Restricting the Mac version to the Apple ID only

On the iPhone restrict Send and Receive to the iPhone Number.

Now manually add your iPhone Number to the New Message on the Mac in the "To" spot (If you try your name it will not pull up your My Card details)

Send the iMessages to the iPhone.

If it does not get sent or get to the iPhone then it is not Logged In.

If that is the case then you needs this Users Tip When the iMessages account will not Login

7:59 pm Wednesday; November 29, 2017

Hi,

I have the same issue after upgrading to High Sierra. I've verified that iMessage on my Mac is logged in to my appleid.

All of my "i" devices are using iOS 11. iMessage work fine on all of them. On the Mac, however, I can neither send nor receive iMessages. I get a "Your message could not be sent." Clicking on "Try Again" produces the same result.

Thanks for any insight you can share.

I'm having the exact same issue. After the latest High sierra update it was working fine but then two days ago it stopped working altogether. No sending or receiving messages on my Mac. I've tried signing out of messages and back to no avail. It's not an icloud problem though, i tested editing a note in my Mac and it was successfully replicated to iPhone.

The problem is whenever I enter a phone number the mac immediately substitutes a name from my contact book.