Why can't I send iMessages to an iPhone from my laptop?

Question

I am using a new MacBook Pro (Retina, 15-inch, Late 2013) with Yosemite 10.10.1 and trying to send text messages to people using the messages app.  Both people I tried to send messages to have iPhones.  I get the same results each time.  You can see by the attached image that I get a red exclamation mark.  When I click on that I get the "your message could not be sent dialog"   Does anyone have any advice for me?

Answer 1

Hi,
It is likely to be something in the Mac User Account.
Messages creates several .plist that start com.apple.ichat
Some refer to the accounts for AIM, Jabber and Yahoo and the Subnet one is for Bonjour.
There is a Shared List one (for Recent Chats that Yosemite's Messages does not display) and the Status Messages one I have posted to Eric about.
This one com.apple.imservice.ids.iMessage.plist deals with calling the info from the Keychain about the item there.
This one com.apple.imessage.bag.plist holds the server info the the iMessages account is logged into.
com.apple.ids.service.com.apple.madrid.plist  is the one that holds the Apple ID used in the  iMessages Account and any other ID linked to that iMessages accounts.
I would delete the last of these and restart the Messages app.
You may have to re-enter the Apple ID.
(And accept the pop ups about the iPhone number)
If that does not work try also deleting the iMessage.bag one as this will force a Server connection when the app is restarted.
If that does not work open the Keychain Access App in Applications/Utilities
With Login in the top left box
Passwords in the lower left selected find the IDS: AppleID iniMesages-Auth token item and delete it (the italics bit will be your Apple ID)
Restart the App again.
Check the Contacts app has your detail in the My Card (Contacts > Preferences > Card > My Card)
After that if it has not worked it is a long process of moving half the listed Apple.com .plists to the Desktop (I would create a folder to hold them)
And then restarting the computer.
You then have to move half the moved ones back to Preferences replacing newer items that have been made if nothing has been solved.
i.e move A to M to the desktop folder. as the apps read the plists you will need to restart.  Then move A to F back so there is a gap between F and N (so you can see where you are up to)
Repeat a 1/2 the reminder until you find the faulty .plist. (complete with restarts each time and replacing new .plist when you move old ones back)
Most likely this will be a group move so you will have to work the last move you made.
This is very time consuming.
If you decide that replacing them all might be the way to go then keep the following:-
Anything with Address Book In it (Some info in in the .plists that you need)
Same for Mail
Any item for purchased apps from Apple Like Pages, Numbers, iWeb and so on as this may contain License info
Do not Delete the Desktop item until you are sure you don't need them and everything is working.
9:47 pm      Tuesday; December 9, 2014
​  iMac 2.5Ghz i5 2011 (Mavericks 10.9)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad