RDP Error: An authentication error has occurred the function requested is not supported . This could be due to CredSSP encryption oracle remediation

 Problem:

Unable to connect server via remote desktop. Getting Error 

"An authentication error has occurred the function requested is not supported .This could be due to CredSSP encryption oracle remediation"

Reason:

This issue will happen whenever you trying to access MS updated server from non updated client or vise versa. Microsoft released the security patches for RDP / CREDSSP which need to install on both client and server.

Solution:

Solution 1: Install latest Microsoft Update patches on Client and Server. This is the recommended and secure solution.

Solution 2: Disable Remote Desktop Network Level Authentication. If you have difficulty to apply solution 1, this option you can use as workaround option till installing latest patches on client and Server.

Steps: 

1. Right Click "Computer", Go to "System Properties", "Remote".

2. Ensure "Allow remote connections to this computer" is checked.

3. Uncheck "Allow connections only from computer running network level authentication" option

Solution 3:

In case you are unable to perform solution 1 and solution 2, example:- You are unable to install the latest patches or you are unable to disable Remote Desktop Network Level Authentication because server is unable to access via RDP or Console, This option you can use as workaround.

Steps:

1: On RDP Client, Open "Local Group policy Management " by typing "gpedit.msc" on START> RUN.

2. Go to "Computer Configuration > Administrative Template > System > Credentials Delegation"

3. Double Click "Encryption Oracle Remediation" 

4. Choose enabled and choose Protection Level as "Vulnerable" 

5. Now you will be able to connect the server by RDP, But strongly recommended to install latest MS patches on both client and Server and revert this changes back to be secure.