Firstly, please make sure you are using WordPress 3.8.x and WP Pipes 1.12.
Secondly, please go to Pipes > Settings and make sure all of system requirements are OK.
If you still see nothing posted, there is something wrong with your pipe configuration, please export your pipe and give it to me, I will test around, correct it and send back to you a working pipe (and you can import it to your WordPress site then).
Learn more:
– How to export a pipe
– How to import a pipe