Error code 5561
Error code 5561 occurs when a brand name that is being provided for a product or brand is already registered and in use on Amazon. This error, and error number 5665, are similar but error number 5665 occurs when a seller inputs a brand name that is not currently registered on Amazon.
For example, Company XXX is registering products on Amazon. If the brand they use already exists, meaning that another busines has already completed the Amazon brand registration process and is actively selling. This will result in error 5561.
Solution: You must obtain permission from the brand owner in order to create and list products in some Amazon categories. Send a ticket using your Seller Central account to accomplish this.