The first step is to make sure you see the actual WSUS server name in the log – if not that indicates a policy or registry setting used for the policy is not in place.
Next get the errors for the client trying to contact WSUS and check the error code against the error code reference for Windows Update agent. For a reference see:

Windows Update information is stored in c:\%windir%\Windowsupdate.log.

Perform the following on the client workstation.
1. Delete the registry keys in
HKLM\Software\Microsoft\Windows\Currentversion\Windowsupdate
2. Restart Automatic Updates service.
3. Issue the command wuauclt /resetauthorization /detectnow.
Updates will start downloading

Removing managed by your system administrator message to update them manually

Set Group Policy Manually
Start -> Run -> gpedit.msc
 
Computer configuration -> Administrative Templates -> Windows Components -> Windows Update
Configure Automatic updates
Choose enabled
Choose option 5 – Allow local admin to choose setting
 
User configuration -> Administrative Templates -> Windows Components -> Windows Update
Remove access to use all Windows Update features
Choose Disabled

After above clients where still not showing up in the WSUS gui after downloading the updates from the server. I checked

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate (SusClientId) which was cloned across all the servers. We had to run this:

Source code

Rem - Batch script to delete duplicate SusClientIDs 
Rem - Implement this script as a "Startup" or "Logon"  script 
Rem - Script creates an output file called %Systemdrive%\SUSClientID.log 
Rem - If the %Systemdrive%\SUSClientID.log is already present, then the script simply exits
 
@Echo off 
if exist %systemdrive%\SUSClientID.log goto end 
net stop wuauserv 
net stop bits 
reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate" /v PingID /f  > %systemdrive%\SUSClientID.log 2>&1 
reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate" /v AccountDomainSid /f  >> %systemdrive%\SUSClientID.log 2>&1 
reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate" /v SusClientId /f  >> %systemdrive%\SUSClientID.log 2>&1 
net start wuauserv 
wuauclt.exe /resetauthorization /detectnow          
:end 
exit