Are you sending your RMA to the manufacturer of the GPU card (MSI, Asus, Gigabyte, etc.) or Retailer or to AMD Warranty at AMD?
If it is to the Manufacturer or Retailer you need to contact them directly to find out what instructions are not being followed since they are the ones that issues the Warranty on your GPU Card and not AMD.
If it is a AMD RMA, What is the RMA number to the claim. Maybe one of the AMD Moderators can take a look to see what is going on or guide you on what to do.
Is your GPU card a Professional or Consumer GPU Card?