Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
What version of windows do you have on your Yoga 2?
Windows 7, windows 8, windows 10?
My apologies, I just seen your messages.
Question, if yu enter the pin incorrectly 2 or 3 times. Does it at any point show you an email address? Probably an email address you own?