During remote connection, the message "due to security error..." is displayed.

Error message: "The client cannot connect to the terminal computer due to a security error. Make sure that you have logged on to the network, please try again to connect to the server ".
 
Cause: If you upgrade the Windows NT domain to Windows 2000 or Windows Server 2003, the certificate on the terminal Server may be damaged. Therefore, the Windows 2000 Terminal service client is denied multiple times when accessing the terminal server.
Solution: In each terminal server and client, perform the following steps:
Create a registry backup on each terminal server.
Navigate to the following registry subitem: HKLM \ SYSTEM \ CurrentControlSet \ Services \ TermServices \ Parameters.
On the registry menu, click Export registry file ".
In the file name box, type exported-parameters and click Save ".

If you need to recover this registry subitem later, double-click the exported-parameters.reg.
Under the Parameters registry subitem, right-click each item on the following values:
Certificate
X509 Certificate
X509 Certificate ID
Click Delete, and then click yes to confirm the deletion operation.
Close the Registry Editor and restart each terminal server.
On the client, create a backup of the MSLicensing registry key and its sub-keys, and then perform the following operations to delete the original and sub-keys:
Navigate to the following registry subitem: HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ MSLicensing.
Click MSLicensing.
On the registry menu, click Export registry file ".
In the file name box, type mslicensingbackup and click Save ".
To restore this registry entry in the future, double-click mslicensingbackup. reg.
On the "edit" menu, click "delete", and then click "yes" to delete the MSLicensing registry subitem.
Close the Registry Editor and restart the client computer.
Warning
Improper registry editing may seriously damage your system. Back up any valuable data on the computer before changing the registry.
Solution 1: If the client still cannot connect to the terminal server, perform the following procedure as an alternative:
Disable the license server.
Disable the license server by using the telephone connection method in the terminal server license server wizard.

When you use the phone option to activate Terminal Server authorization, Terminal Server authorization uses other certificates.
Create a registry backup on each terminal server, and then delete the Certificate, X509 Certificate, and X509 Certificate ID Registry Entries in sequence, as described during execution.
Close the Registry Editor and restart each terminal server.
On the client, create a backup of the MSLicensing registry key and Its subitem, and then delete the original and subitem, as described during execution:
Close the Registry Editor and restart the computer.
When the client restarts, the missing registry key is re-created.
Solution 2:
This may also be caused by selecting "full security mode" when adding "Terminal Server.
The solution is to delete "Terminal Server" in "Add/delete programs"> "Add/delete windows components", add a new terminal server, and select "loose security mode ", restart your computer.
This article is from the "VirtualWay" blog