1. It really helps if your PC that has Playon installed on has AT LEAST a 3gb cpu. It takes alot of memory to stream/transcode web media content.
2. It will work with a less robust PC - but just not as well and you should have 1gb of memory available too ( on the Playon PC)
3. After you install the software (trial was yours, correct?) the very first time you try to connect from your Android you MUST do it over a WIRELESS connection. This is very critical to further use of this.
4. In Playon settings, make sure you enabled Netflix with your accouts username and password. Same goes for Hulu, Pandora, etc.
5. Microsoft IE 8 (with Silverlight installed ) is supposed to be required to avoid
a "stream not found / null" error - which sounds like might be what you are encountering.
I upgraded my PC to all of the above specs and even upgraded my wireless router to one that can stream UPNP/dlna media content (Linksys e 3000)
If you have any other issues, let me know. Been there, done that