Hello,
On the server side...
I am assuming you have already enabled AD enrollment from Directory settings, if not please enable the setting Enroll using directory synch option under directory synchronization settings.
On the client Side....
While the package download please make sure you select the customize option before downloading the package from SEMS,
Check the below registry stamp and make sure that package already installed is managed by same universal server. Once confirmed please perform a re-enrollment with server once again.
To check PGP STAMP registry
32-bit systems: HKEY_LOCAL_MACHINE\Software\PGP Corporation\PGP
64-bit systems: HKEY_LOCAL_MACHINE\Software\Wow6432Node\PGP Corporation\PGP
PGPSTAMP value
ovid=keys.example.com&mail=notesmail.example.01&admin=1
Steps about how to re-enroll Symantec Encryption desktop is mentioned in below tech note.
http://www.symantec.com/docs/HOWTO42029
Also any other enrollment related troubleshooting is also given this tech note.
http://www.symantec.com/docs/TECH149341