Why does Chrome say "Your connection to this site is not secure" even if the certificate is valid?

I found what it was. After updating Chrome and restarting it, the lock sign was fine. Chrome did not mark my site as insecure anymore. However, as soon as I accessed my server on another port with a self-signed certificate, and I accepted browsing despite the self-signed certificate warning given in Chrome, my site got marked as insecure, even on the tab where I was accessing the standard port (443).