Do you have this issue.
Duplicate accounts: You can only have one AdSense account. If you’re found to have a duplicate account you’ll have to decide whether to use your existing account to monetize your channel or to cancel it.
Website Issue: To monetize a YouTube channel, you’ll need to complete your AdSense sign up directly from YouTube Studio. Do not create a new account from the AdSense website using a URL unless you intend to monetize that site.
Check Video solution here.
To fix Duplicate Account follow below steps:
1. Get and scan government approved ID Card.
2. Create a fresh gmail addresses or use any one without Adsense.
3. Login to your YouTube account.
4. Click on the Youtube studio.
5. From the left side scroll to monetization page.
6. Open monitization tap and check for Setup error.
7. Click on Associate your Account.
8. Select has no account.
9. Verify your own youtube account.
10. It will take you to the new gmail account created earlier.
11. You need to complete the new gmail Adsense payment address and sometimes upload ID Card.
12. Click Associate the Account.