Mac network accounts are user accounts that can be set up to access multiple Mac computers on a small, medium or large network. Although many users have no problems with accessing their account on any Mac computer on the network, some may encounter a "Network accounts are unavailable" message when attempting to log in. There are four primary causes for this error message and if you understand each potential cause you can generally resolve the network accounts unavailable message on your Mac.
Macs that are managed through network accounts are typically a part of a large environment, such as a school or other business. As such, the Mac network account usernames are typically displayed as email addresses. If your Mac network has recently been updated, either due to an OS upgrade or patch, the way these usernames are entered may have changed. For instance, users who previously entered their Mac network account username as firstname.lastname@example.org may now have to enter their username as yourbusiness\yourname or else they will be given a "Network accounts are unavailable" message.
Recent OS Upgrade
Although network accounts are a feature common to every new version of the Mac OS, occasionally they may not be initially compatible with the newest version of the OS. Users who have recently upgraded to a new version of the Mac OS X may find that their network accounts are no longer available due to the upgrade. When the "Network accounts are unavailable" message is displayed due to a recent OS upgrade, it can typically be fixed by either downgrading the Mac to an older version of Mac OS X or by installing a patch released by Apple to correct the problem.
When a network or other administrator binds a Mac to a network, the Mac can be managed through Active Directory. If binding has failed, the user may receive a "Network accounts are unavailable" message when attempting to log into the Mac because it no longer recognizes the network. Many users resolve the issue by unbinding and then rebinding the Mac on their network. After rebinding the Mac and rebooting the computer, the "Network accounts are unavailable" message usually disappears. Users can consult the user manual for their Mac for instructions on performing this process.
Occasionally, the "Network accounts are unavailable" message may occur because the name of the Mac computer is not recognized on the network and therefore the network cannot access the Mac. This is usually because the Mac's computer name has either been intentionally or accidentally changed by the user. For most users, resolving the issue merely requires updating the computer name and host name in System Preferences, the Open Directory Utility and through the Terminal application so that the computer name and host name are the same in all three places. Users can determine how to do this by consulting the user manual for their specific Mac.