Hello,

I would suggest you to  - 

• Go to the Administrators under Admin tab.
• Check the Online status in the right pane for the desired administrator visible under View Administrators.
• If the status is Offline then the Windows Latest Symantec version under Virus Definitions Distribution will be blank.
• Create a new admin user in SEPM under the Admin tab with System Administrator rights.
• Log in with the new Admin credentials.
• Check the Online status in the right pane for the desired administrator visible under View Administrators.
• It should show as Online.
• If we do have proxy settings, follow  this Article: https://www-secure.symantec.com/connect/articles/how-configure-proxy-settings-symantec-endpoint-protection-manager-sepm-121

Now check the Windows Latest Symantec version under Virus Definitions Distribution in the Home tab.

It should be visible.

Also, check the IE Enhanced Security -

1. Launching the Windows Control Panel.
2. Open Add or Remove programs and click the Add/Remove Windows Components button.
3. Disable the Internet Explorer Enhanced Security Configuration option, and then click Next.
4. Upon completion of the Windows Components Wizard, click Finish. You may need to restart the computer for the changes to take effect.

Again, check this Article: https://www-secure.symantec.com/connect/forums/proxy-changes-liveupdate-121

Hope that helps!!