Based on what I've seen at the lines at SFO, I'd say you're SOL. Use Easy Checkin. Use Curbside Checkin. Anyone I've seen miss their flights and have to go to the ticket buyers line where I'm standing to redeem a cert is so fumed and I ask them if they tried checking in with the machines and they say no. I ask if they considered using the SkyCap and they so no. I'd say - it's your own fault.