Hi,
This is a common error code for failure of remote connection and you could kindly check following.
From Windows computer (target machine to be remoted to ):
1.Confirm if the RDP has been enabled. If the user account has been added into the allowed users.
2.Check firewall and anti-virus tool in case of any blocking setting for the RDP connection.
From Mac side, here is a suggestion to check the temp folder of Remote Dekstop (MAC Only)
Please refer to method 6 for more details.
https://appuals.com/remote-desktop-error-code-0x204/
3.Try to clear and fill in the info again when starting the remote connection.
Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny