Please do these steps this will resolve
1. Make sure that proxy settings are correct, in the SEPM.
2. In the Proxy server, add a rule to allow traffic from the computer that hosts the SEPM server.
3. In the proxy Server, add a rule to allow traffic from liveupdate.symantecliveupdate.com
4. Also, allow traffic from the computer hosting the Proxy server itself.
5.Configure proper DCOM settings:
-> On the Windows taskbar, click Start > Run.
--> In the Open box, type the following text:
dcomcnfg.exe
--> Click OK.
Expand Component Services, and then expand Computers. Right-click My Computer, and then click Properties. On the Default COM Security tab, under Access Permissions, Edit Default.
---> The Access Permission pane is normally blank. If the window is not blank, make sure that the Administrators, Interactive, and System accounts are set to Allow Access. .
SAMEER