Cannot open SSL It! extension in Plesk: Error 500 idn_to_utf8: empty domain name: U_ILLEGAL_ARGUMENT_ERROR

Symptoms

• Unable to open SSL It! extension for a domain in Plesk Panel:

  idn_to_utf8: empty domain name: U_ILLEGAL_ARGUMENT_ERROR

• Domain has invalid NS records:
  

  # dig NS example.com +short
  ns1.example.org
  ns2.example.org

Cause

Invalid NS records for the affected domain. An item for improvement for the error message parsing was created with ID #EXTSSLIT-1919 

Resolution

Remove the invalid DNS records on the DNS registrar side.