Keychain Access can occasionally bug out and create issues. This happens especially when you upgrade your macOS or switch to a new Mac. While the Migration Assistant is an amazing tool, we’ve seen that if you chose to defer dealing with Keychain Access, the Messages app sometimes stops working correctly. You can still receive messages (iMessages as well as SMS), but you’re not able to send messages from your Mac. When you try to send, you will get a red exclamation in a circle saying “message could not be sent, try again.”
Before you get frustrated, try this quick fix:
Close the messages app & press command + Q and click on the messages. A applications window will pop up so just open your iMessage from there. Works sometimes. Oct 18, 2019 iMessage is the Apple messaging service you get automatically with your Apple ID. If it's not already set up, you're asked to sign in when you first open the Messages app. Sign in with same Apple ID that you use with Messages on your iPhone and other devices. Your Apple ID is the account you use for all Apple services.
Open Keychain Access either through the utilities folder or Spotlight Search
Navigate to the File menu and select “Lock Keychain ‘Login'”
Navigate to the File menu again and select “Unlock Keychain ‘Login'”
You’ll be asked to enter your Mac password
Enter the password and try to send your message again
Hi,
Open a Finder window.
Message App On Macbook Not Working
Use Go Menu whilst holding down the ALT key at the same time.
This add the Library to the Menu list.
Select it.
Navigate to Preferences.
Find com.apple.iChat.plist
Messages App Mac Won't Login Email
Drag this to the Trash Restart Messages.
If this does not help then start up Font Book.
Check you have and have them Activated:- Helvetica Neue, Lucida Grande and Emojies (Apple Color Emojies are near the bottom of the list).
8:28 pm Monday; February 12, 2018
iMac 2.5Ghz i5 2011 (Sierra) G4/1GhzDual MDD (Leopard 10.5.8) MacBookPro 2Gb (Snow Leopard 10.6.8) Mac OS X (10.6.8), iPhone 6 iOS 11.x and an iPad (2)