After applying DS records on a Plesk server the website does not resolve anymore: loading from master file example.com failed: at top of zone

Symptoms

• The Glue records are set up on the DNS registrar pointing to NS in Plesk.

• The following messages can be found in /var/log/syslog as well as on systemctl status bind9 output:

  named[504]: example.com: DS record at top of zone (zone.example.com)
  named[504]: zone example.com/IN (unsigned): loading from master file example.com failed: at top of zone
  named[504]: zone example.com/IN (unsigned): not loaded due to errors.
  named[504]: all zones loaded
  named[504]: running

Cause

The DS records of the main domain should be placed on the registrar-side.

Resolution

Update the DNS records on the registrar-side and add the DS record there.