So I sold some of DD's AMerican Girl doll clothes, packed up securely, used the printed out label from Paypal/USPS. According to the tracking info the item was delivered on Dec 22 but now the buyer says it was never received and has opened up a case
I responded through the Ebay dispute resolution page but I'm not sure what to do next. Do I contact USPS, does the buyer or do both of us? If Ebay finds against me do I have to issue a refund and am I out the $25 that the buyer paid?
TIA for any help!

I responded through the Ebay dispute resolution page but I'm not sure what to do next. Do I contact USPS, does the buyer or do both of us? If Ebay finds against me do I have to issue a refund and am I out the $25 that the buyer paid?
TIA for any help!