How many get invites and how many walkons do they take? I recall watching someone's backstory - the guy had failed in Kansas City or something and then his wife or girlfriend told him, "You're going to Pittsburgh." I don't remember if that meant he waited in the walkon line and didn't get picked or he failed the course in Kansas City.
I would think you would definitely not get a second invite if you failed. Possibly you could get a walkon - not sure about that.