The warranty is nothing to do with Amazon, it is a promise from the manufacturer.
Did you buy it from Amazon or a business seller using Amazon marketplace?
Under the relevant legislation, the goods must be fit for purpose and of satisfactory quality.
If a fault shows within the first 30 days the seller must give a full refund; within 6 months the seller (Amazon) must either attempt a repair or offer a replacement. If he can't do either he must refund.
After 6 months the buyer must show there was an inherent fault (not broken by the buyer or misused). So you would need to get an independent report saying it has stopped working because there was a defect when it was made. If your claim is successful the seller can deduct an amount from the refund to reflect the amount of use you have had from it.
Your argument is with the manufacturer who is refusing to honour the warranty. Do you have the warranty to refer to? Is there any mention of 'preferred sellers' particularly on the box?