Cannot issue free certificate in DigiCert SSL or SSL It! extension in Plesk: File authentication failed. File not found

Symptoms

• Issuing a free certificate in Plesk either in Domains > example.com > DigiСert SSL > Basic SSL > Activate now or in Domains > example.com > SSL/TLS Certificates > Symantec Encryption Everywhere > Complementary DV > Select (if the extension SSL It! is installed):

  PLESK_ERROR: Something went wrong with your order. Please double check configuration parameters. File authentication failed. File not found

  ---

  PLESK_ERROR: Could not issue an SSL/TLS certificate for example.com
  Details
  File not found.

• There is no A record either for example.com or www.example.com or they resolve to an IP which is not Plesk:

  # dig +short example.com
  #

  ---

  # dig +short www.example.com
  #

Cause

DigiCert verifies both www and non-www domain’s name and fails if one of them could not be resolved.

Resolution

Set up a DNS record for hostname example.com or www.example.com, so it is resolved over DNS properly.

If Plesk DNS server is used check the article How to add a DNS record for a domain in Plesk?

In case an external DNS server is used, it is required to add the records on Registrar side.