We would like to know more. Go here: https://www.youtube.com/features > Click on monetization and share the screenshot of the page that you see. This would help us look into the issue better!
If you were eligible and applied before June 1st, then you should have received an email and update in Creator Studio with more information. If your application is being held for an additional review, then you'll get a second update in the near future: https://goo.gl/2icqfh