I've sold 3 pairs of tickets on Stubhub for an event which uses Ticketmaster. The Ticketmaster event said it would deliver the tickets 48 hours beforehand. When I logged on 46 hours beforehand, all six tickets are in my Ticketmaster account and have QR codes. However, the Transfer Ticket feature is not available.
Now I don't have the option to screengrab the QR code and do a mobile upload. So, I've got the emails of all three buyers, I have QR codes/tickets in my account and yet I have no way of getting the buyers their tickets.
If you sold them with a delivery method of transfer, you'll have to contact StubHub customer service and let them know they have to be delivered as a mobile upload. However, I do believe the customer has the option to cancel the order. In that case, you'd be liable for a selling fee penalty.