Even after following all the steps from Github, I still not able to have the plugin working. Here's all I did:
1) Created a subdomain in my server and configured a SSL server block in nginx: https://push.ipodschool.com/
2) Checked the .htaccess and verified that the equivalent nginx rules were applied and must be working fine.
3) All other details, including the certificates uploads, the details in the config file were checked. PHP is working (https://push.ipodschool.com/helloworld.php). MySQL is also working.
However, I still get blank pages in index.php, desktop.php instead of viewing the main index that may show everything is working. As consequence of it, the plugin doesn't work and Safari doesn't pop up to the reader the option to accept push notifications.