Just got approved for an authorized 2nd selling account last week…

I opened a case and that was about all it took.

You might want to give it a try also:

Greetings from Amazon Seller Support,

I’ve reviewed your e-mail and understand your concern regarding the second selling account.

In this case, please be informed that, if you have a legitimate business need for a second selling account, you can apply for an exception to this policy. On the Contact Us form, select “Account Settings” and then the “Other account issues” sub-category:

https://sellercentral.amazon.com/gp/contact-us/contact-amazon-form.html

To apply for an exception, you must:

1. Provide an explanation of the legitimate business need for a second account
2. Have an account in good standing with excellent Customer Metrics
3. Have a separate e-mail address, credit card, and bank account for the new account
4. Not intend to sell the same products in both accounts

You’ll receive a response to your request within 2-3 business days.

If you have any concern regarding this, please write back to us and we’ll assist you further.

Have a nice day!

Please let us know how we did.

Thank you for selling with Amazon,

Rhaswa D.
Amazon.com Seller Support