A. Examine the expiration date on the certificate on the origin site. Validate that the certificate has not expired. Replace the certificate if necessary.
B. Examine the hostname on the certificate on the origin site. Validate that the hostname matches one of the hostnames on the CloudFront distribution. Replace the certificate if necessary.
C. Examine the firewall rules that are associated with the origin server. Validate that port 443 is open for inbound traffic from the internet. Create an inbound rule if necessary.
D. Examine the network ACL rules that are associated with the CloudFront distribution. Validate that port 443 is open for outbound traffic to the origin server. Create an outbound rule if necessary.