Can't Reset screen lock pin

My wife was forced by the nexus to put a pin on the screen lock. Now she can not remember the pin. She has face recognition, so she can get in it but when we try to remove the face/ping lock we fail because of the pin. Instructions on the net say to keep trying and you will be given a chance to reset via her google account. Problem is it never gives us forgotten pin prompt. Any ideas, we really don't want to hard reset. Any ideas why it never prompts us to reset the forgotten pin? Thanks