Client machines created from an image with a duplicate client ID appears only once in the WSUS admin console. Each client must have a unique ID generated for each individual installation. WSUS admin console will display only one client for each unique ID. If you have multiple clients created from an image that share the same ID, only one appears in the WSUS admin console. All clients will check in and receive updates, but only one will appear and display the status in the WSUS admin console. In cases where clients do not check in, and they were created from an image, the following steps will restore the existing duplicate client ID.
a. Run regedit and go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate
b. Delete the PingID, SUSClientID and the AccountDomainSID values
c. Stop and start the Wuauserv Service
d. From the command prompt run: wuauclt /resetauthorization /detectnow