“No returns” on eBay does not apply if the buyer claims the item isn’t working or described properly.
‘EBay does not inspect items claimed as such and takes the buyers word. They will immediately allow the buyer to print a return label charged to you.
Essentially, eBay allows any sale to be voided, the seller gets the item back, the buyer gets all of his money back and the seller pays shipping both ways. It can happen on virtually any sale on eBay. Kind of “no harm/no foul” only the seller eats shipping and any damage/misuse/etc. to the item.
If you refuse to accept the cartridge back, the buyer will get the cartridge AND all his money back. You might even get charged a 3rd time for shipping it back. That would REALLY piss you off! Take it back and sell it locally to reduce your loss.
‘Despite all this, for me it is rare to have a buyer do this, but it has happened to me. That’s just part of selling on eBay. (It works great if you’re a buyer.) It can get really expensive for items that cost a lot to ship. So I am not doing those on eBay.