5461 error Help UK/USA Amazon

I own a brand in the UK and have recently set up on amazon.com (usa)

I have 2 products in my UK Store; I have successfully added 1 product and send a test batch of 30 units to amazon FBA in the USA which have all sold quickly.

Amazon.com won’t allow me to add my second product. I am presented with the error 5461, but when I follow the instructions from amazons email on how to resolve it, it doesn’t work.

When logged in to Amazon USA and I add new product to inventory I search using the barcode number and the ASIN and it can’t be found. Despicte an email from Amzon stating” we have found that the product is already available in our 6 (jp) store.”

How can my first product be found and added but my second listing isn’t findable?

I have a pending trademark application in the USA and a actual trademark in the UK. Both UK and USA trademarks are added to my brand registry account. My amazon.com account is added and approved on my brand registry account for selling my brand.

How can this be resolved as I cant talk to anyone at Amazon other than automated email which offers the same advice that doesn’t work.