I updated my macbook pro to OSX Mavericks and signed in to Messages app but it isn't working. My account is enabled but when I try sending a message it says cannot send message. Your iMessage account isn't signed in. Not sure what's causing the problem, any help?
Have you tried deleting your iCloud account (which includes your iCloud account in the messages app) and re-adding it? There might be a stale config file somewhere that just needs to be re-created. Try either removing/re-adding your entire iCloud account or just unchecking/checking the "Messages" option under your iCloud account in System Preferences.
I would 1st go to the Apple Website and verify your AppleId login Credentials. double check your updates, sometimes they all dont update until another one has finished.
Blow out your old Account info in messages. and Add a new account with your current apple ID. if you still have issue. login as root user , nuke old account, Run permission repair, log back in as JoeUser and create Account in messages. -x