It's not just ebay/PayPal that won't accept prepaid cards, any prepaid cards, even prepaid debit cards issued by specific banks as directed by the Fed. Govt. - as in SS debit cards. There are many companies using online purchase software, (Instacart is an example) that will simply not accept them. And it doesn't make any difference what you're buying, they won't accept them for any purchase. I've had it happen to me numerous times. And no, I don't why they won't accept them, nor have I ever been able to find a reason, they just won't accept them.
Same thing happened to me this year and I was so furious and tried selling my gift card to an online shop but I figured out a work around, you might lose a few bucks but you’ll get money to spend.