I tried this yesterday with my new platinum card number I got from the 100k mile deal. It said the same thing. I called the concierge for Amex and she looked into it and found out the CIID I had didn't confirm for her. She checked with the new cards people and said that they told her the CIID I was given on the webpage was temporary and "wouldn't work with all charges." She seemed a little baffled by the explanation and apologized, but said that my new card was rushed and would be here Wednesday and it should work then. I just saved my GE app online and will complete it today.
Just for the data point, here on the east coast with Dulles airport the appointments are pretty easy to come by based on the experience some of my friends have had.