I'm not sure whether this needs to go here or in the Linux hosts forum...
I have a Linux server running Debian 8.10 running VirtualBox 5.1.30 in which is a Windows 2012 server client which has the remote desktop server enabled on the standard port of 3389.
I have been perfectly able to connect to it using the remote desktop client in Windows 10 and so everything appeared to be OK in terms of the configuration.
Santa, in his great generosity, brought me a 27" iMAC

but I find I am unable to connect to the remote desktop server provided by VirtualBox. I have tried both the Microsoft Remote Desktop Server (v10.1.0) and also RoyalTSX. The former aborts with error code 0x204 and the latter just sits there spinning its little wheel attempting to connect.
Is there something special that is needed either in the VirtualBox configuration or in the macOS RDP client?
-Andy
My crystal ball is currently broken. If you want assistance you are going to have to give me all of the necessary information.
Please don't ask me to do your homework for you, I have more than enough of my own things to do.