License was not automatically updated on Plesk: KeyUpdate Result code: 2 Network failure

Symptoms

• Plesk license was not automatically updated on a server with one of the following messages:

  PLESK_WARN: Warning: You are currently operating within the grace period of your product license. To update your product license, select the Retrieve Keys option on the License Management page.

  ---

  PLESK_WARN: Your license key has expired. To continue using your Plesk, you must purchase a non-expiring commercial license key.

• The following message is received by Plesk administrator:

  Unable to update EXT.12345678.1234: an error occurred while processing your key. You can try to retrieve the key manually in Plesk (Tools & Settings > License Management) or let Plesk try to update it in the next 24 hours. If you do not want to receive this notification any more, remove this key from Plesk.

• The following errors can be found in the /var/log/plesk/panel.log file:

  ERR [panel] KeyUpdate Result code: 2 Network failure
   ERR [panel] KeyUpdate Result desc: Not valid XML. XML parsing failed

  ---

  ERR [panel] KeyUpdate Result code: 2 Network failure
   ERR [panel] KeyUpdate Result desc: Not valid XML. no element found

  ---

  TLSv1.2 (OUT), TLS header, Certificate Status (22): > SSL data removed for security reason
   * TLSv1.2 (OUT), TLS handshake, Client hello (1): > SSL data removed for security reason
   * Unknown SSL protocol error in connection to ka.plesk.com:5224 * Closing connection 0 cURL verbose output:
   * Could not resolve host: ka.plesk.com * Closing connection 0

Cause

The corrupted file /etc/sw/keys/registry.xml or Plesk licensing server (Key Administrator) is overloaded with the same requests.

Resolution

Apply one of the following solutions, depending on Plesk configuration: