I had similar experiences at ORD this past weekend. They were definitely all aware that the Prestige cards have access.

First time, at the G concourse AC they spent a lot of time and ultimately were able to get it to work apparently by putting in my card number, deleting my name and then proceeding in their system?? Something like that, they tried to explain it to me for the future. They were very nice about it all at least...

Second experience, at the H/K AC the woman checking me in swiped it, scanned my boarding pass, and told me I was all set. I asked if it had worked correctly and she grumbled something to the effect that it didn't, but at least she was familiar with how to make it work.

This sums up the Prestige in a nutshell - a little screwy but great benefits when you can get them to work.