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Step 9 - check if new server has been installed or network configuration has changed like DNS or authentication changes or even patches have changed on client server.
The last April 9, 2024, the patch KB5036896 was released by Microsoft. My recommendation is to be careful to install this Windows Update on Agent machines since it is causing potential connectivity issues when establishing a valid session between the Gateway and Agent machines. The KB5036896 is affecting badly NTLM authentication especially when Kerberos is not available in the target machine, and consequently, the connectivity is being interrupted at some point between Agent and Gateway generating unexpected behavior or server unavailable issues. Besides that, this patch is also affecting DC (Domain Controllers) and VPN connections.
If you notice interruptions in the connectivity, please check if the KB5036896 is installed in the Agent machine, and if so, please uninstall it and reboot the machine to get rid of issues caused by the patch. Don't install it until Microsoft released a patch that fixes the issues mentioned above.
A list of other possible patches causing issues per Windows editions here:
Windows Server 2022 (KB5036909)
Windows Server 2019 (KB5036896)
Windows Server 2016 (KB5036899)
Windows Server 2012 R2 (KB5036960)
Windows Server 2012 (KB5036969)
Windows Server 2008 R2 (KB5036967)
Windows Server 2008 (KB5036932)
For more information about known issues related to this patch, please visit the following links: