Branded product listed as Generic

Hello everyone.

I am a new seller on Amazon UK.
There’s a product that is listed on Amazon UK with brand “Generic”. However, the product clearly belongs to a specific brand. I purchased a few units of the product from a wholesale supplier thinking that since the product is listed under generic brand, anyone could sell on it. But when I try to add my product to the listing I get this error:

We have identified that you were attempting to contribute (for example, change detail page, create or update offer) to this generic ASIN. If you want to make changes, such as extending this ASIN to a new store, creating a new variation relationship, updating ASIN attributes or adding offers to sell the product, you can create a new ASIN by following the process as outlined in our Add a Product tool. For more information, go to Amazon’s Generics policy .
If you believe you are compliant with our policy, contact Selling Partner Support and mention the error code 5885. When you contact Selling Partner Support, provide the following information:
• Product title • Marketplace ID • SKU • ASIN • If you are using inventory file templates, provide the batch ID of the inventory file process report.

I am totally unable to understand the whole situation. I request senior members to kindly help me with a couple of queries:

1. How could someone list as Generic a product that has the brand name clearly printed on the bottle as well as the box plus there’s a barcode on the actual product as well but if we search this barcode in Add a Product it shows no results.

2. If, by whatever way, someone has managed to list this branded product as Generic then how come I or anyone else cannot add their product on this listing since it is “Generic”?

3. How can I get around it?

Thanks