I am not here to make excuses or anything, but when you uploaded your receipt, you should have initially uploaded the amended receipt from Amazon. The Step up process goes off of the receipt loaded to your account, which shows that you originally purchased from a 3rd party reseller. No matter who fulfilled the order in the end, your uploaded receipt still shows an invalid seller which is what EVGA must go off of.
I have never seen EVGA try to find ways out of honoring the Step up process if the card was purchased from an authorized resales from the beginning, the card was registered within the alloted time frame, the receipt was uploaded, and the request submitted for step up.
I am sorry to see you going through these frustrations after waiting so long.