Cloudflare cannot resolve the origin web server’s IP address.
A missing DNS A record that mentions origin IP address.
A CNAME record in the Cloudflare DNS points to an unresolvable external domain.
The origin host names (CNAMEs) in your Cloudflare Load Balancer default, region, and fallback pools are unresolvable. Use a fallback pool configured with an origin IP as a backup in case all other pools are unavailable.
When creating a Spectrum app with a CNAME origin, you need first to create a CNAME on the Cloudflare DNS side that points to the origin. Please see Spectrum CNAME origins for more details
How to resolve
To resolve error 1016:
Verify your Cloudflare DNS settings include an A record that points to a valid IP address that resolves via a DNS lookup tool.
For a CNAME record pointing to a different domain, ensure that the target domain resolves via a DNS lookup tool.
Common cause of this error.
Cloudflare cannot resolve the origin web server’s IP address.
How to resolve
To resolve error 1016:
Referred from cloudflare doc here