I purchased a theme, which is no longer supported and is totally broken. How do you get your money back? Should someone be responsible for selling something that does not work, and the author keeps taking money?
Can you share the item URL?
If you are eligible to get a refund then you can request for a refund. Can I Get A Refund is an explanation of the refund policy.
What happens after you have requested a refund? This article explains what happens next, how long your request might take and how the procedure works: