Thanks Mike. I appreciate that.
I can't speak to why your RDP server is not responding within the ~15 seconds that Guacamole waits for connections to be established. If the server was just started, it likely simply isn't ready to accept RDP connections at the time the attempt was made.
How can we make sure that RDP server isn't ready to accept RDP connections ?
This is not only happening if server was just started but if user connects once and again try to reconnect after an hour ( any time ...)