I would also like to know how to revoke my GCKey, because it's not at all obvious.
Also, the error message makes little sense.
Your answer is incomplete. Provide the necessary information below to continue.
The name, date of birth or country of birth you entered for your signature does not match the name you entered in your Online Application. To submit this Online Application, the names must match. Only the applicant can electronically sign this Online Application.
I did not have to provide my DoB or CoB for my signature, so why does it mention these two options? I had to select "I agree" (which happens to be the only option) and I had to provide my given name(s) and last name. I've checked many times that the provided name matches up with the name on my application. I've even tried many of the suggestions in this thread, such as using all caps, leaving out one or both of my middle names, and so on.
I still have to try revoking my GCKey, but according to others, sometimes that doesn't work either.
It's bad enough that the government uses closed and proprietary public-facing documents (e.g. you have no choice but to download the latest version of Adobe Reader, because the contents of the application form differ depending on which PDF viewer you use).
P.S. If anyone from CIC happens to be reading, please redesign all application processes with usability as top priority. Currently the user experience is awful, almost as if it was designed to be a deterrent.