Buyers claiming not receiving packages

Hi, seller here. I have lots of claims from buyers saying the package wasn’t delivered even though tracking proves it does. Then, with those, amazon auto refunds them. I open a SAFE-T claim which worked before in trying to get reimbursed, but in these recent months, amazon does not cooperate with me anymore even when i attach usps tracking proof. they just say the order is non returnable, but that does not matter at all because i deserve a reimbursement since i didn’t do anything wrong as the seller. do any of you guys have tips in general with dealing with these customers?