Trust self signed Cert in Chrome macOS 10.13

From your description, it seems to me that you have installed the certificate as a simple X.509 certificate, but have not set it to be trusted for SSL.

To do that, from the keychain, reopen the certificate, expand the Trust section, and change the SSL setting to "Always Trust"

Close the dialog to save the changes (you’ll be prompted for your password again). If you refresh the browser window you should see the happy green lock:

If you don’t see the green lock, just restart Chrome or type chrome://restart into the address bar.

To troubleshoot this kind of problem, open Developer Tools, go to Security tab, and you will see why Chrome deems the certificate invalid.

It is likely to be due to its lack of subjectAltName extension.

You can remedy this by following these steps: https://stackoverflow.com/a/56530824/2873507