Have you tried contacting them? I understand that even if you can't sign in, the "help" message form at the bottom of the NaNoWriMo home page will work.
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Regards,
Eric Fretheim
Assistant Prep Leader, 2015 October NaNoWriMo Prep Challenge

"It is perfectly okay to write garbage-- as long as you edit brilliantly." ~C.J. Cherryh

“No, writing 50,000 words in a month is normal. You are not crazy. This is not insane.” ~Teri Brown