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. Also, share the channel URL, as this would help us look into the issue better!
Thanks for the screenshot! You should have received an email and a notification with more info in Creator Studio. Take a look at those resources and note that you can always reapply for the YouTube Partner Program again in 30 days.