From the screenshot it looks like Pega Installer is unable to connect the postgres database server. There can be many reasons like -
1. The Hostname or Port that you have specified is incorrect.
2. The connectivity from unknown clients to the database has been blocked either at Firewall or Database server. Or in other words the IP address of the client (system where you are running the Pega installer) may not be whitelisted on the database server.
As next steps you should contact your database server admin to confirm / rectify if any of the above two problems are occuring.
To validate a successful connection issue the following telnet command.