There are several reasons why your AdSense for YouTube application may have been disapproved, and the most common disapproval reason is because your application is a duplicate of an existing account. Our policies only allow one account per user and it's against the AdSense Terms and Conditions and AdSense for YouTube Terms of Service, as applicable, to create a second account.
If you receive an email from us saying that your application has been disapproved for being a duplicate, you may associate your original account with your YouTube channel. The email will provide details about your original account.
Learn more about the common reasons why applications for AdSense for YouTube accounts are disapproved in our Help Centre.