You must sign in with your Apple Account (formerly Apple ID) to use iMessage on your Mac or sync your iPhone texts to it. It’s a simple process, but in some cases, you may see random errors that prevent you from logging in. Go through these quick tips if you see “ An unknown error occurred ,” “ Error with Authentication ,” or another similar message when signing into the macOS Messages app with your Apple Account. Make sure you’re entering the correct details If you type your Apple Account email address and password incorrectly, the app should display the appropriate message. But in some cases, it will simply throw the generic “An unknown error occurred” text in red color on the screen. Therefore, double-check that you’re entering the correct details. In case you have forgotten your Apple Account password , reset it quickly from iOS Settings or macOS System Settings.…