Plesk restart failure: Failed to list unit files: Connection timed out error

Below is given an image of plesk opening failure.

One of the error messages is given below.

    WARNING!
    Some problems are found during start service httpd(see log file: /var/log/plesk/rc_actions.log)

    Continue...

    /usr/local/psa/admin/sbin/pleskrc execution failed:
    Failed to list unit files: Connection timed out

CAUSES

    This is caused when services fail to start because of high CPU usage by systemd

RESOLUTION

   1. Connect to the server via SSH.

   2. Create a directory:

       # mkdir /root/example

   3. Move session files from /run/systemd/system:

       # mv /run/systemd/system/session-.scope /root/example/

   4. Restart services from the error message:

      # service sw-engine restart
      # service drwebd restart

   5. Restart the upgrade.