Check your settings
Make sure the date, time, and time zone are set correctly in Apple menu System Preferences Date Time. You can also select “Set date and time automatically” to keep this information accurate.
If third-party firewall or port filtering software is installed, it needs to be configured to allow connections to apple.com, verisign.com and verisign.net. See the list of ports required to use Messages and FaceTime and get help using FaceTime and iMessage behind a firewall.
If your /private/etc/hosts file has been modified, make sure that it isn’t interfering with communications to apple.com, verisign.com, or verisign.net servers. Some third-party software installers might modify the /private/etc/hosts file without alerting you.
Get more help resolving issues with a /private/etc/hosts file.
