Tasks in Plesk are never executed and stuck as new: Cannot fetch process properties

Symptoms

• Various tasks in Plesk are never executed, they are stuck as new at Tools & Settings > Task Manager page.

• The following error can be found in /var/log/plesk/task-manager.log file:

  ERROR 2022/09/04 Cannot fetch process properties: Cannot fetch 'run-plesk-task-93137.service' unit properties: dbus: connection closed by user
  

Cause

Stuck dbus.socket service.

Resolution

1. Connect to the server via SSH.

2. Restart dbus.socket and plesk-task-manager services:

   # systemctl restart dbus.socket plesk-task-manager

Warning: at Debian 10 or Ubuntu 18.04 there might be polkit service, which also should be up & running. Restart it with systemctl restart polkit in case the issue persists on these OSes.