Restart the postgres server from the terminal for ubuntu
sudo service postgresql restart
then it will dispay the results of the cause for failure e.g
2015-05-08 17:33:46 EAT FATAL: private key file "/etc/ssl/private/ssl-cert-snakeoil.key" has group or world access
2015-05-08 17:33:46 EAT DETAIL: File must be owned by the database user or root, must have no write permission for "group", and must have no permissions for "other".
so you can use the
chmod 740 ssl-cert-snakeoil.key
or access the file by navigating through the folders, right click the file and change permissions to the postgres administrator
Thanks, your good to go.