Out of nowhere this week, all of staff at one of clients reported that they were getting this error when remoting-in to their on-premises remote desktop server from offsite:
“Your computer can’t connect to the Remote Desktop Gateway server. Contact your network administrator for assistance.”
And they did!
While looking through all of the services set to Auto on their RD Gateway machine, I noticed that the SQL services weren’t running (the SQL services are not a critical component on this VM so we weren’t monitoring their running state). When I tried to start the SQL services, I found this in the Application Event Viewer:
“The server was unable to initialize encryption because of a problem with a security library. The security library may be missing. Verify that security.dll exists on the system.”
While pursuing that issue, I found this: https://blog.sqlauthority.com/2017/03/14/sql-server-errorlog-server-unable-initialize-encryption-problem-security-library/ – TLS 1.0 was disabled in the registry. Enabling TLS 1.0 allowed the SQL services to start and it let users connect to the RDS server, too!
Hope this helps somebody else!