In my case (macOS High Sierra, Chrome 66) the cert was still invalid resulting in error message: ERR_CERT_COMMON_NAME_INVALID
The solution was to add some extra parameter as described here: https://stackoverflow.com/questions/43665243/invalid-self-signed-ssl-cert-subject-alternative-name-missing
After that and adding the cert again to the keychain (and setting the trust right) the SSL cert went green eventually.