International Brand Registry Question

I am reaching out to gain clarity on a Brand Registry issue. Our brand is currently registered with Amazon Spain. We have an Amazon Spain Store front. We have started to sell our brand in the United States the past few months and would like to also be brand registered in the US so that we can create an American Amazon Store front and other content for our products. We created a US Seller Central account and started the Amazon Brand Registry process and was initially approved after submitting the verification code from the trademark lawyer, but then denied.

Amazon-

“Your Brand Registry application has been declined as we have identified the trademark from your application as related to a brand that is already enrolled in Brand Registry.”

To access the enrolled brand, we recommend that you contact the brand administrator who may add you to the enrolled brand as an authorized user and may also add any additional trademarks to the brand’s profile.”

My question is HOW do I do this? After I gain access as an authorized user am I then able to connect my Seller Central Account and start to build the American Brand Store Front? I want to make sure I understand the process so I can clearly communicate it to our brands team in Spain.

I have 9 years of experience selling on Amazon, however, I have never had such a hard time finding a clear answer. Maybe I am missing something but I have searched the seller forums, googled this issue, emailed brand registry, and spoken with my Amazon contacts and I haven’t gotten anywhere. I know there is an answer I just can’t find it. Any guidance is extremely appreciated!