If you're not able to install any updates, then there must be a problem in getting updates from WSUS Server.
1) Ensure that client certificate is distributed from correct WSUS Server.
2) Check if the policy is correctly configured to the client machine, You can verify WSUS registry key values (HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate). If not, Configure the policy setting using "Windows Update Local Policy Management" option in PatchManager
3) When the configuration has been confirmed, first launch the "Detect Now" task, wait for the completion of the detection event, then execute "Report Now" task.
4) Finally, Run Windows update scan on the client machine to see the applicable 3rd party Updates and install.
