Hopped on my iMac this morning and suddenly I can no longer text my wife on her iPhone from my iMac. After a minute or so of poking around, I got it fixed.

I clicked on Messages, then Accounts, and saw that iMessage was greyed out. Somehow my iMessage account disabled itself. It’s an easy fix.

In the Messages app:

1. Click Messages
2. Click Preferences
3. Click the Accounts Tab
4. Select your iMessage account
5. Re-enter your Apple ID and/or password
6. Enable this account should be checked

And you should be all set!