Why won’t eBay allow me to refund my customer through PayPal?

Description

I mailed a bathing suit to a buyer and unfortunately it got lost in the mail and I did not choose a shipping option that included tracking information (I now realize this was a huge mistake). However, I want to refund the buyer as soon as possible to avoid any further conflict with them and eBay as well, I also just want to refund the buyer because it is the right thing to do since I am the one who chose to send the suit without tracking information. When I try to refund the buyer through eBay, I just receive the message that there was an error with my refund and to check with PayPal to see what the problem is. I have checked everything on my PayPal account and eBay account to make sure they are linked but I am still receiving this error message. If anyone has suggestions of what I need to do, or something that I may have overlooked, please let me know. Any suggestions at all would be greatly appreciated. Thank you in advance for any responses!