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I'm reaching out regarding the pulse oximeter I purchased. It arrived in new condition with all packaging intact, but unfortunately, it doesn't seem to function correctly. The screen remains blank despite confirming that the battery is fully charged and inserted properly. I've checked for any signs of damage and everything looks good, but the device is not operational. Given these circumstances, I suspect it may be defective. I would like to initiate a return process for a replacement unit. Please let me know how to proceed with this request. Thank you for your assistance!