I had the same experience as Victoria. I was accepted after going from 1 hub to 3.
Also, it should say the reason in the e-mail they sent you saying you were not approved, at least mine told me the reason. Mine said,
I bet that adding pictures and/or videos to hubs will help to add more of the content Google is looking for.
If the issue wasn't insufficient content, then I can't help you, but I'm sure plenty of the hubbers here can!