Hi,
Please do the following and I think you sshould get through.
To install clients using the 'Find unmanaged clients' tool in Symantec Endpoint Protection Manager, follow the below steps:
1. Click the Clients tab in the Symantec Endpoint Protection Manager
2. In the left pane select Find Unmanaged Clients under the Tasks.
3. In the Find Unmanaged Computers window you can search for the clients two different ways:
a. Using an IP address range
b. Using the Computer name
4. Fill in the login credentials for the workgroup or domain that the clients belong to and click Search Now.
5. After the clients have been found in either Unmanaged Clients or Unknown Clients select the ones that you wish to add.
6. Specify the Client Install Package, Installation Settings, and Features.
7. Install to that Group by selecting Start Installation.
Please check this link as well
http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2007120609232248
To install an unmanaged client:
Using your serial number, download the installation files from
https://fileconnect.symantec.com.
Right-click the file you downloaded and click Extract All.
Click Next.
Select the location to which to extract the files, ensure that Show Extracted Files is checked, and click Finish.
For 32 bit Operating Systems, in the folder that contains the extracted files go to CD1\SEP\.
For 64 bit Operating Systems, in the folder that contains the extracted files go to CD1\SEPWin64\x64\.
Double-click Symantec Antivirus.msi.
Follow the on-screen prompts to complete the installation of the unmanaged client.
Please revert in case of any help.