A negative feedback killed my sales

[fredslist]

Hello everyone,
A few months back, I sold a watch and when the buyer received the item, he left a negative feedback on my page without contacting me. In his feedback, he said that the quality of the item was poor. I have sold the same watch before and never received such a critic. I'm a relatively new seller on the platform. Therefore, my feedback score went from 100% to 97,3%. With such a score, my sales have completely halted. I'm struggling to sell a single item. When my feedback score was 100% my listings were placed in the first or second search page. Right now I can barely find them. I tried so many things to get back on track. Nothing seems to work. I didn't know we were able to contest a negative feedback, it's too late right now because the comment was left more than 30 days ago. Has anybody been in such a situation? If so what can I do to improve my status and make more sales? Should I buy some item to improve my feedback? Should I stop selling for a year?

Any help will be immensly appreciated.

Thanks!