Install libpam-x2go by entering the following commands in the terminal:
sudo apt update sudo apt install libpam-x2go
PAM Module to check credentials against X2Go servers
Auth and session PAM module that uses SSH to authenticate against an X2Go server as the remote host and user. Local account required. . This PAM module is intended for facilitating Remote Logon into X2Go Session using LightDM's Arctica Greeter.