Hello,
Is the machine connected to Internet? Are the MAC clients Managed?
If Managed, check the Liveupdate Settings at SEPM and also check if the MAC is able to communicate to SEPM properly or not?
If Unmanaged, then to schedule a time to automatically update your virus definitions with LiveUpdate:
- From the Applications folder, open the Symantec Solutions folder and select Symantec Scheduler.
- In the Symantec Scheduler window that appears, click New.
- From the window that appears, choose Product Update.
- In the text box, enter a name for the task, such as Update virus definitions daily .
- From the pull-down menu under "Choose a product to update", select Virus Definitions.
- From the pull-down menu next to "Set a Frequency", choose Daily.
- Using the text box and/or the up or down arrows, choose a time of day for the update.
- Click Save, and then close the window.
Symantec Endpoint Protection will run LiveUpdate automatically at the day and time you set. LiveUpdate will use your existing Internet connection.
Also, Check this Article: Symantec Endpoint Protection for Macintosh Frequently Asked Questions
http://www.symantec.com/docs/TECH134203
Hope that helps!!