Unable to login Message on Mac, "An Unknown Error Has Occured"

I realize that these run-of-the-mill responses are helpful for people who haven't tried anything at all to fix the problem on their own. But, for those of us who've already gone through the list -- and the problem persists -- we need more assistance than these types of answers.

The problem is well-documented online so it would appear to be a problem with Messages on OSX.

Any other suggestions on how to resolve this error? It's affecting productivity.

Hey, just wanted to chime in here and say that resetting the NVRAM worked for me. Thanks!

what does an unknown error mean.i have signed in with a known correct password but it will not accept it

Hello deejayjj,

It sounds like you'll need to take these related steps for a solution to signing in to iMessage on your Mac: If you can't sign in to your iMessage account or FaceTime on your Mac

If you can't sign in to your iMessage account or FaceTime on your Mac

If you can't sign in to your iMessage account or FaceTime, one of these solutions might help.

When you first set up Messages on your Mac, you're asked to sign in to your iMessage account with your Apple ID. Messages then automatically attempts to sign in every time you open it. Signing in to FaceTime is similar. If either app doesn't sign in successfully, try these solutions. 

Check your internet connection

Make sure that your Mac is connected to the internet. You should be able to load web pages or receive email, for example.

Connect to the internet with your Mac

Check for a service outage

Check for any temporary service outages affecting iMessage or FaceTime.

Apple System Status

Check your Date & Time settings

Make sure that the date, time, and time zone are correct.

Set the date and time on your Mac

Make sure that your software is up to date

Software updates can improve the stability, compatibility, and security of your Mac, and might also resolve the issue.

Update macOS on your Mac

Check your Apple ID

To make sure that your Apple ID and password are correct, go to the Apple ID account page and sign in with the same Apple ID that you're using with Messages and FaceTime. If you're able to sign in, open the app and take these steps:

* Messages: Choose Messages > Settings (or Preferences), then click Sign Out. Sign in again with the same Apple ID you used on the Apple ID account page.

* FaceTime: Choose FaceTime > Settings (or Preferences), then click Sign Out. Sign in again with the same Apple ID you used on the Apple ID account page.

Reset NVRAM

In case the issue is related to any of the settings stored in NVRAM:

Reset NVRAM on your Mac

Check for third-party software

If you installed firewall, security, VPN, or other third-party networking software, make sure that the software isn't blocking any of the network ports used by iMessage and FaceTime. If necessary, disable the software and then try using your iMessage account or FaceTime again.

Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues

Learn more

If FaceTime isn't working on your Mac

FaceTime is not available in all countries or regions.

You may also need to confirm your settings for Handoff for the iPhone and Mac: Use Handoff to continue tasks on your other devices

Hoping this helps out.

Take care.