Unable to create subdomain in Plesk: plesk-task-manager service might not be running

Symptoms

• Unable to create subdomain in Plesk:

  Domain sub.example.com creation failed:
  Cannot connect to the task manager (plesk-task-manager service might not be running): No such file or directory

• plesk-task-manager service is not running:

  # systemctl status plesk-task-manager.service
  ● plesk-task-manager.service – Plesk Task Manager Service
  Loaded: loaded (/lib/systemd/system/plesk-task-manager.service; disabled; vendor preset: enabled)
  Active: inactive (dead)

Cause

Disabled plesk-task-manager service.

Resolution

1. Connect to the server via SSH.
2. Enable and start plesk-task-manager service:

   # systemctl enable plesk-task-manager.service && systemctl start plesk-task-manager.service