The warning shows up when your server is not very well configured for making HTTPS connections to other servers. During installation process your server performs a test HTTPS connection. If there are any problems with that, then a special flag is set in config.php (verifySSLCertificates=false) to ignore verification of SSL certificates. Things you can do to fix this:
- check if your system CA database (certification authorities) is up-to-date …especially if you’re using an older, not updated OS.
- check configuration of your php-curl, because it may use wrong (or empty) database of CAs.