In an effort to thwart "bad actors" who hijack listings with generic versions of your product, Amazon has instituted some safeguards that, while troublesome at first, are in the best interest of 3P sellers. Here is what to do if you get the ERROR CODE: 5665.
I hope that you have not listed "NA", N/A" or "Generic" in the Brand Name field while listing your product. While brand registry is not required to sell on Amazon, this is something that you should strive for in order to give your product line more legitimacy with shoppers. This is achieved through the Amazon IP Accelerator Program. You will also need to acquire barcodes for your products. These can be obtained via UPC/GTIN from GS1 website, or via Nationwide Barcode.
The ERROR CODE: 5665 is Amazon's way of making you verify that you are the brand owner and have authorization to sell on that listing. Here are the steps you need to follow to resolve this issue:
On the selling platform, go to Help>Help Adding a Product>Call ME>Amazon Will Call You>Or Email Them. You need to be prepared to provide a photo of your product, product with logo, logo, and your product packaging with logo. Another way to verify your ownership of your brand could be the submission of a website URL link. Once Amazon validates brand ownership, you should have smooth sailing ahead!
Again, this may seem like a PITA to navigate but in the long run, these hoops that Amazon has implemented will help keep riff-raff off of your listing. This could save you from poor reviews caused by hijackers who have flooded your inventory with knock-offs.