Go to your Cancellations screen.
https://www.ebay.com/sh/ord/cancel
You can see 90 days of sales on your All Orders Screen.
https://www.ebay.com/sh/ord/?filter=status:ALL_ORDERS
Look for the transactions with $0.00 dollar amounts. That indicates a refund.
Otherwise, go to your Managed Payments screen to see orders older than 90 days.
https://www.ebay.com/sh/acc
Download report(s) and look for transactions with $0.00 amounts.