Q: Can't activate iMessage on iMac with El Capitan

Hi Alex_h1,

I'm having exact same problem. However when I tried to delete the account in iMessage on my iMac the " - " or delete option is not available. Any additional advice appreciated!

Messages – Can’t log in

It sounds good, but no dice on my Mac Pro tower.   I can't successfully sign into iMessage, and preferences are not available when I'm not signed in, so I can't delete and re-add my account from Messages.  There was a link to a number of other threads that purportedly address this situation, but none of those solutions have worked (deleting plists, force quit in IMAgent, etc.).

Basically, signing in with my AppleID works for everything (including this forum) except for messaging on my Mac Pro (just upgraded to El Capitan).  Messaging works fine on my iPhone and iPad.  I disabled messaging there, and reenabled, and it still works fine - but no luck on the Mac Pro.

Simply put, when I sign into Messaging (the authentication screen says iMessage), I cannot successfully log in.  I get an authentication error (the username and password supplied are correct).

Sadly, while that worked for an iMac, it doesn't work for a Mac Pro (tower, not a MacBook Pro).  It all worked fine before I upgraded to El Capitan.

Thanks! Just got around to following up. I tried this once, but misread. Tried today and worked fine! Thanks again!

Hi,

It is interesting that this gets a Helpful as it is incorrect.

In Messages, choose Messages > Preferences > Accounts. Select your Apple ID in the left column, and click the minus icon below the list of accounts.

You cannot delete either the iMessages Account or the Bonjour one.

Same here.

The iMessage account can only be Sign out of or have the "Enable this Account" box unticked.

NOTE.
It is also annoying that the list cannot be re-ordered by dragging the Accounts up and down the list like before.

8:42 p.m.      Wednesday; October 7, 2015

Help! None of the above have helped me, and I'm having the same problem. Apple ID works just fine, but not with Messenger. Keeps redirecting me to iCloud settings where I can't change anything, basically. All I get is "An error occurred during authentication". NO mistyping, NO problems with network etc. What, in the world, is going on here?

Hi,

There is a sort of "history" to this.

At OS X 10.8.2 update Messages became version 7.0.1

This required that the Serial Number was on the Mac (See the "About this Mac" item in the Apple icon menu).

The Serial Number is usually missing if the Mother/logic board has been replaced (refurbishment or repair) and someone forgot to "put it back".

It can be put back at an Apple Store with an App they have to do so.

In the app you got a big pop up warning there was a Login issue and to contact Apple Support and a code number to give them.

Later it was discovered that during Mavericks and Yosemite that there are at least two versions of where the Account in Messages looks logged in but fails to send.

The first turns all Contacts red  in the "To" spot and tell you they are not registered with iMessages.

The second allows you to "send" but immediately the "Not Delivered" response shows up.

For these we have been suggesting people contact Apple Support, get moved to a Level 2 person by explaining that they have a Apple ID issue with the iMessages server for their Mac.

Initially this seemed to work.

Now the Level 2 people want to do much more testing and eventually call in the Engineers and promise to call you back.

The Account then seems to work the next day without a further phone call.

Each device creates a unique login to the iMessages server.

The Mac uses the Password and Serial Number to create the IDS: AppleID-Auth Token seen in the Keychain.

It is because of this unique login that the ID works on other devices or in other apps without issue.

It would appear that it is a security feature to protect you from others trying to be you (someone could have your ID and Password but still can't pretend to be you from another Mac - it's not really that simple but in essence it is what is being aimed for).

Obviously the engineers want to know why this happens.

Now we have it happing at the Upgrade and some Update OS changes.

The only route after checking everything else is to contact Apple Support.

Nothing I have suggested to people recently have made anyone at Apple Support resolve the issue any faster.

8:16 pm      Friday; October 30, 2015

I notice you have not included the padlock icon which 'ungrays-out' the minus symbol you are claiming cannot be edited.

Thats why! you have to click the padlock icon which is not in your screenshot.

Hi,

That's interesting.

I have checked my Preferences > Accounts again and clicked each in turn.

My Main AIM account and my Google Account both have greyed out Minus icons but not Padlock.

In addition the iMessages and Bonjour Account also remain this way (greyed out Minus iCon) which is as I expected.

Could you post a picture please ?

8:14 pm      Friday; November 6, 2015

I continue to see a very similar issue (can't activate iMessage on my Mac), despite working with Apple support for almost 2-weeks.  Everything other than iMessage works fine, and messaging works on my iPad and iPhone.

This is a new issue with El Capitan - worked fine with Yosemite.  Suffice it to say, despite all the help in this forum, and engineers from Apple working on it, for me the issue continues.