SSL Certificate Name Mismatch: NET::ERR_CERT_COMMON_NAME_INVALID

The certificate is valid, unexpired, and CA-signed — and the browser still refuses it with NET::ERR_CERT_COMMON_NAME_INVALID, because it was issued for a different hostname than the one you typed. Why the Common Name no longer counts, the causes in the order they bite, and how to read the SAN list your server actually presents.