Recently it was necessary for me to enable XRDP service on Ubuntu 20.04 VM, so I followed the steps outlined in one of my old posts and get it working quickly. Unfortunately I run into some new issue with not being able to reset or shutdown Hyper-V VM for some reason, which I ignored for now, but after couple of power offs I realized that I cannot connect via XRDP until I open session locally. I then decided to check on the service status with sudo systemctl status xrdp command and got the output shown below:

Full error message says: [ERROR] Cannot read private key file /etc/xrdp/key.pem and I’m pretty sure that it didn’t show up when I used the same status command after initial configuration, though people tend to forget and miss things 🙂
Anyhow to clear up this the following command has to be executed:
sudo adduser xrdp ssl-cert
Abovementioned error occurs when the default user for XRDP’s service lacks access to the directory to which /etc/xrdp links, and with the command above you allow the user xrdp access through ssl-cert group membership. I hope that this information may come in handy to some one else 🙂