Problem connecting to xrdp (windows 10 ->ubuntu 14.04)

I have a Windows 10 laptop trying to RDP into an Ubuntu 14.04 desktop.

I installed TightVNC on the ubuntu station, then installed xrdp, basically following the instructions on this page

When I launch RDP on my Windows laptop and try to log in, I get the following error:

connecting to sesman ip 127.0.0.1 port 3350
sesman connect ok
sending login info to session manager, please wait ...
xrdp_mm_process_login_response: login successful for display
started connecting
connecting to 127.0.0.1 5910
error - problem connecting

On the ubuntu side, the entry in the /var/log/xrdp-sesman.log has:

[20190128-12:00:18] [INFO ] scp thread on sck 7 started successfully
[20190128-12:00:18] [INFO ] ++ created session (access granted): username user, ip 192.168.1.100:52303 - socket: 7
[20190128-12:00:18] [INFO ] starting Xvnc session...
[20190128-12:00:28] [ERROR] X server for display 10 startup timeout
[20190128-12:00:28] [ERROR] another Xserver is already active on display 10
[20190128-12:00:28] [DEBUG] aborting connection...
[20190128-12:00:28] [INFO ] ++ terminated session: username user, display :10.0, ~~~

Where would this error be coming from?

I already tried reinstalling tightvncserver and xrdp in the order suggested in another forum.

sudo adduser [username] xrdp