As a dedicated seller on your platform, I recently sold a Samsung Galaxy Watch Ultra to a buyer for $300. The item was shipped via UPS and confirmed to have been delivered by both USPS and UPS, albeit one day late. I have obtained proof of delivery documents from both carrier agencies.The day before the scheduled delivery, the buyer contacted me via the Mercari app, expressing an intention to return the watch but mentioned that she might wait to see if it would arrive the following day. Upon its arrival, the buyer stated that she needed to return the item because she had already purchased the same watch elsewhere. Shortly after, I received a notice from Mercari indicating that a return had been initiated.I wish to highlight that, according to Mercari's policies, all sales are final unless there is an issue with the item. The buyer subsequently claimed that she had not received the package, contradicting her earlier statements and the confirmation from both USPS and UPS.Despite numerous attempts to resolve this issue with Mercari's customer support, I have been met with responses that have only added to my distress. One of the latest messages I received from Mercari confirmed that my package had been delivered. However, my funds have still not been released. I later received an apology from Mercari stating there was a mix-up, as they thought I was the buyer.Given the evidence provided by both USPS and UPS, and the buyer's initial acknowledgment of receiving the package, I am unable to comprehend why my funds have not been released. This situation has caused me significant stress and financial hardship.