IPv6 HTTPS handshake failed
An AAAA record exists, but the HTTPS handshake to that address failed.
Why it matters
Resolvers will hand clients an address that does not complete TLS.
What to do
Serve a valid certificate on the IPv6 address, or remove the AAAA record until it works.
Reference
Modern public sites should be reachable over IPv6 with the same TLS guarantees as IPv4.