I have sent in a couple of apps for publisher network and keep getting rejected. Nothing out of the ordinary for the sites. I dont get it.
There's plenty of people who've applied years ago, when it was first announced, and haven't been accepted. Hopefully it's because YPN is looking for sites that are needed to test specific things.
Read around this forum some. It's very hard to get accepted right now, I even read that they aren't accepting any new applications at this time. You'll probably just have to wait for it to come out of beta which doesn't look like any time soon from what I see. Just go with google adsense or something similar for now.
It takes forever, and countless tries to get into YPN. Try again, and just keep on working on your site.