Well any time you decide to cut it close, things often go wrong. You must be *checked* in, even on the kiosk, 30 minutes before the flight. I've had times where the time on the kiosk was a couple of minutes different from mine, and that will cause problems, as well.

Obviously if you had not forgotten your OLCI you would have been fine as well. I would have *certainly* not waited until 19 minutes before the flight was leaving to finally catch an agents attention, even if they were busy with someone else. A polite, "Excuse me, my flight leaves in 31 minutes, and this kiosk isn't letting me check in", usually works.