Some actions fail in Plesk: "Cannot connect to the task manager" or "Unexpected non-whitespace character after JSON"

Symptoms

• An operation in Plesk fails with one of these error messages:

  PLESK_ERROR: Cannot connect to the task manager (plesk-task-manager service might not be running): No such file or directory

  PLESK_ERROR: Internal error
  SyntaxError: Unexpected non-whitespace character after JSON at position 96 (line 1 column 97)

• Plesk Task Manager service is in the "Activating" state:

  # service plesk-task-manager status | grep Active
  
  Active: activating (auto-restart) (Result: exit-code) since Wed 2025-02-26 06:50:18 UTC; 1s ago

• The following error messages are logged in journalctl for service plesk-task-manager:

  # journalctl | grep plesk-task-manager | tail -n 20
  
  plesk-task-manager[1022672]: 2025/11/11 08:12:10 Cannot open '/var/log/plesk/task-manager.log' log for writing: open /var/log/plesk/task-manager.log: permission denied

• The following error messages are logged in /var/log/plesk/task-manager.log:

  CONFIG_TEXT: ERROR Failed to update DB schema: unable to open database file: permission denied

  CONFIG_TEXT: Cannot connect to the task manager (plesk-task-manager service might not be running): No such file or directory

Cause

Plesk Task Manager installation files have incorrect ownership.

Resolution

1. Connect to your Plesk server via SSH.

2. Set correct permissions for Plesk Task Manager directory and subdirectories recursively:

   # chown -R psaadm:psaadm /var/lib/plesk/task-manager/

3. Set correct permissions for Plesk Task Manager log:

   # chown -R psaadm:psaadm /var/log/plesk/task-manager.log

   # chmod 0640 /var/log/plesk/task-manager.log

4. Restart plesk-task-manager service:

   # service plesk-task-manager restart

5. Verify that the service is active now:

   # service plesk-task-manager status | grep Active
   
   Active: active (running) since Wed 2025-11-11 10:03:09 UTC; 8s ago