CredSSP encryption oracle remediation [Authentication Error]
If you are experiencing the following error with your Remote Desktop Connection,
"An authentication error has occurred. The function requested is not supported
This could be due to CredSSP encryption oracle remediation."
Cause of the error
The "CredSSP encryption oracle remediation" error relates to a change Microsoft rolled out in their May 2018 Windows Updates. This requires that both the client machine (the machine you are connecting from) and your server – to have the latest updates.
You will need to update your server to the latest Windows updates to resolve this. The steps below will help you connect to your server in order to update it.