OK, I've just now heard back from the NokiaUSA supervisor's supervisor. They verified that the agent did tell me the code was valid (and I'm sure he believed it was! the ad appeared to say it would be as well). They let me know that perhaps a new code would be released to rectify the situation. I'm not sure if that's only in my case (i.e. you may need to complain if you're in this situation as well), or if it'll be more broadly available. In any case, I'll post what I learn here.