The issue is a account conflict between the developer account and the other account. If you have signed up with 1 account and trying to set up another account, the account conflict will cause the issue.
Here are the steps to resolve this:
Sign out of App Store and iCloud from the first account where an older developer account exists
Delete the developer app which is linked to the first account on App store.
Sign into app store with the new account
Download the Developer app with the new account details and sign into
Sign into iCloud with the developer account
Once you finish these steps you will be able to complete your enrollment.
Good Luck.
QilaIO
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