If you opened a return through Ebay, you had 21 days after starting the return to ask Ebay to step in.
After all of this time, this is between you and the seller.
If it is a business seller, they may have an address you can write to or a phone number you can call to chase up your refund.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)