Hi @Ky4271p
Stubhub is a reseller site. Your buyer originally bought on a primary site such as Ticketmaster or Axs. When you accepted the tickets what site were you sent to? If you go back to that site such as AXS or Ticketmaster and log in you should find your tickets and then be able to transfer to your buyer.
After you transfer the tickets dont forget to confirm the transfer in your open sales on Stubhub as this lets them know the transfer has occurred. I would recommend keepng the email you get from Ticketmaster or AXS as proof of transfer