Wordpress install on heroku, accessing pages non root pages, server configuration
Please check your permalinks settings, it should be configured so that index.php comes in your url. The reason behind it is that on nginx server index.php is required in url,
try your url with index.php for ex if your post url is xyz.com/helloworld, then in post url check with xyz.com/index.php/helloworld.
The issue is with urls try changing permalinks and set to include index.php
/index.php/%postname%/use custom permalink option with above setting.