Confirm port 80 accessibility
Ensure the following:
Port 80 is open and publicly accessible on the web server
Firewall rules do not block DigiCert IP addresses. See IP addresses DigiCert uses for the HTTP Practical Demonstration check.
Geographic filtering does not prevent DigiCert from accessing the validation file
If HTTP Practical Demonstration validation continues to fail after confirming all of the above, use a DNS-based validation method instead.
What's next
Order and manage certificates in CertCentral to begin requesting certificates after completing domain validation setup