“High Sierra won’t send iMessages. Since I have High Sierra installed, I can’t send iMessage. It shows “Not delivered”, but incoming messages works properly. I did try to turn on and off iMessages, restart, activate two-factor authentication, but it still doesn’t work.”
Zedex70 from Apple Communities
The Messages app for Mac allows you to send unlimited messages to other Mac devices and iOS devices via iMessage. However, after updating to High Sierra, the latest operating system for Mac computers, some users noticed that High Sierra won’t send iMessages from the Messages app and all iMessages returned “Not delivered” error immediately after they sent the messages. They have tried the general troubleshooting steps including quitting Messages app, restarting Mac, signing out of Apple ID and signing back, and so on, but none of them did the trick.
If you find Mac Messages app to be not sending iMessages in High Sierra, read on to get 2 solutions to fix the problem.
How to Fix High Sierra Not Sending iMessages
Method 1. Remove Incompatible Keychain entries
After system update, the corrupt or incompatible keychain entries could be the cause of High Sierra not sending iMessages. In this case, you can fix the problem by removing the related keychain entries with following steps:
1. Close Messages app.
2. Open Keychain Access under the Utilities folder of your Applications folder.
3. From the list of keychains on the left side of the window and select Login and select All Items under category list.
4. Search for entries of IDS and delete all entries that has IDS.
5. Search for entries of FaceTime and delete all entries of FaceTime.
6. Search for entries of Messages and delete all entries of Messages.
After delete all these related keychain access entries that might make High Sierra won’t send iMessages, you should be able to get Messages app work correctly now. If it doesn’t work, you can try resetting NVRAM or PRAM on your computer.
Method 2. Reset the NVRAM/PRAM
NVRAM (nonvolatile random-access memory) stores some certain settings like sound volume, display resolution, startup-disk selection, and more on with your Mac computer. On older Mac computers, similar information is stored in PRAM (Parameter RAM) instead of NVRAM. And you can use the steps for resetting PRAM and NVRAM.
1. Shut down your Mac.
2. Turn on your Mac and immediately press these four keys together: Option, Command, P, and R.
3. Hold those keys down until your Mac reboots again and you hear the second startup chime.
4. Release the keys and let your Mac reboot normally.