Ubuntu 18.04 || Remote access - remote server display not supported

I've been running anydesk and teamviewer on my headless ubuntu (18.04LTS) box for a while now (over 6 months) without issue. I had to set up an xorg.conf to allow things to run headless over anydesk or teamviewer. I've had an issue crop up in the last week where anydesk will display the error remote server display not supported and refuse to connect. If i plug the box into a screen, it will allow it to connect. I've seen others with the same issue being attributed to wayland, but when checking my desktop session is running in X11 so its not wayland.

Any idea where i should start?

This was very well answered at the following link, which worked for me: Anydesk remote server display not supported e.g Wayland

After installing Anydesk on my Ubuntu 18.04 server and trying to connect from a Mac, I would get a display_server_not_supported error. I was able to resolve this by going into the /etc/gdm3/custom.conf file and changing:

[daemon]
    # Enabling automatic login
    AutomaticLoginEnable=true
    AutomaticLogin=$USERNAME

After rebooting the Ubuntu server, Anydesk now connects and shows the login screen and I can login just fine.