Check your licenses in SIM (Symantec Installation manager) If they show expired call Symantec Support and open a licensing case to renew and combine your licenses.
Then apply the licenses by performing the following steps:
1. Open SIM (Symantec Installation Manager)
2. Click on "Add/Update licenses"
3. Click "Install licenses" button
4. Browse to the directory where you license files are located
5. Select all license files and click "Open"
6. Click "Yes" button on confirmation window
After that you should be promted to restart Altiris Services and after restarting services licenses should be applied. You can check the license status in "Add/Update licenses" window.
If you are using more than you purchased it can cause a problem too. You can purge or retire old machines to reclaim their licenses.
http://www.symantec.com/docs/HOWTO95111 - Best Practices for Retiring Computers