Amplify custom domain shows "Available" but CNAME is not resolvable from authoritative nameservers

Hello, I'm experiencing an issue where an Amplify-hosted app shows a custom domain as "Available" in the Amplify Console, but the domain is not actually resolvable at the DNS level.

1) Situation Summary

• Root domain: lhe.co.kr (managed by an external DNS provider, with nameservers: dns1.cscdns.net, dns2.cscdns.net)
• Subdomain: mes.lhe.co.kr
• The custom domain (https://mes.lhe.co.kr) has been added to AWS Amplify, and the status in the Amplify Console shows “Available” with SSL issued and managed by Amplify.
• In the DNS settings of the domain provider, the following CNAME records are configured:
• The domain ownership validation CNAME (_***.mes.lhe.co.kr) is also properly registered and confirmed.

** 2) Problem Behavior**

• Although the Amplify Console shows the domain status as "Available", accessing https://mes.lhe.co.kr in the browser results in a DNS_PROBE_FINISHED_NXDOMAIN error.
• Running a direct DNS query shows that the CNAME is not resolvable from the authoritative nameserver

3) What Has Been Verified

• The ownership verification CNAME responds correctly.

• The mes CNAME is visible in the DNS management UI, but does not respond from the actual nameserver.

• DNS record has been saved properly, and it's been more than a few hours since configuration.

  4) Questions

  A. When the Amplify Console shows "Available", what criteria is it using to determine the domain's status—does it only check the ownership validation CNAME?

  B. In this situation, is there any way on the Amplify side to perform additional configuration, verification, or force a re-synchronization? (e.g., triggering a re-validation manually)

  C. Are there known causes or best practices for avoiding state mismatches between Amplify and external DNS providers (non–Route 53), especially for subdomain setups like this?

I’m happy to provide further configuration or logs if needed. Thank you in advance for your support.