Windows Server Update Services (WSUS): WSUS previously known as Software Update Services (SUS), is a computer program and network service developed by Microsoft Corporation that enables administrators to manage the distribution of updates and hotfixes released for Microsoft products to computers in a corporate environment. Please see How to disable unused Cisco Access Ports, Windows server update services: Guide, and Client Visibility Issues: Fix WSUS Clients appear then disappear in the console.

This happens most times because the servers are created from an AMI (never syspreped). For more information on PowerShell and USOClient commands, see https://techdirectarchive.com/2020/02/05/handy-windows-server-update-services-commands-wauaclt-powershell-and-usoclient/, How to apply Windows Updates from WSUS to the server using AWS RunCommand,

Note: All other servers are reporting to WSUS such as Windows Server 2008R2 and Server 2012 R2 but Windows Server 2016 does not.

Note: Server 2016 creates all registry keys, and the WSUS server connects with the Windows server.

Reason for this Error?

Delete the SusClientID and SusClientIDvalidation keys from the registry. This is because the server was created from a clown (AMI) and new ones will be generated automatically.

Please see how to Configure SSL between WSUS servers (Upstream and Downstream Servers), Handy WSUS Commands, Windows Server Update Services Commands, WAUACLT, PowerShell and USOClient, How to Start, Stop and Restart Windows Server Update Services (WSUS) via PowerShell and CMD, and WSUS clients appear and disappear from the WSUS Update Services console.

Fix Windows 2016 Servers do not show up on WSUS console

Stop Windows update service, and delete SoftwareDistribution folder

C:WindowsSoftwareDistribution folder

Run the commands below from the command line

wuauclt /resetauthorization /detectnow

And this as well

wuauclt /detectnow /reportnow

For more articles, I have written see the following links below

Configuring WSUS Email Notification to Work With Office365
How to setup and configure Windows server update services (WSUS)
Important Areas to Master on WSUS (Installed and not applicable, Install 1/4, and Installed / Not applicable 100), and
Targeting WSUS Client with the Registry keys: How to configure WSUS Clients to get Updates from the WSUS server using Registry.

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