The Trust Relationship Between This Workstation And The Primary Domain Failed
There are a number of reasons this can happen - basically it means that the Domain Controller and the Server are not communicating. For example, if a domain controller goes down and the server brought up, it cannot communicate to authenticate the server in the domain. This can also happen when system recoveries are necessary or when restoring a Virtual Machine.
One method (though not the best) is to simple login to the server as an Administrator, go to the System Properties, leave the domain by specifying a temporary workgroup name (you'll need the AD Administrator account & password), reboot then join the domain again.
However, there are two better ways to do this by simply resetting the Server Password in Active Directory from the Server you are having issues with. Login as the Server Administrator then via a Command Line (using Run as Administrator), enter the following:
netdom.exe resetpwd /s:<AD server name> /ud:<user name> /pd:*
Reset-ComputerMachinePassword [-Credential <PSCredential>] [-Server <String>]
Where 'PSCredential' is the login name and 'String' is the name of the domain controller. For more info on the PowerShell command, see here:
Once either of these methods are used, I suggest rebooting the server - when it comes back up, login with a domain account.