Error in Plesk logs: Unable to get key: Repository is not opened

Symptoms

• An error appears in /var/log/plesk/panel.log every day:

ERR [panel] Unable to get key: Repository is not opened

• Permissions on /etc/sw/keys/ directory and files in it are set accordingly to the Error in Plesk: SWKeyExFatalError: "Cannot open file" or "Permission denied"
  article.

• registry.xml files is present and solution steps from Plesk does not open: SWKeyExFatalError Repository is not opened do not take any effect.

Cause

Plesk bug with ID #PPPM-13853 which will be fixed in future updates.

Resolution

As a workaround, the error can be safely ignored.