I have had this same issue crop up. No warning just one day my password doesn't work. Oddly, my password on the pc was never the same as my Ms account, the hotmail I have it linked with, so when it told me to reset via the live account reset link I was a bit dubious.
Nevertheless I gave that a try, amended my password and still nothing. Called ms helpdesk who helpfully advised that I leave it connected to the internet and wait. 24 hours. So I wait about 36 before calling again. They couldn't help but offered to let me buy an upgraded care subscription, then he would escalate it. I refuse to pay to get what can only be a glitch in windows ten resolved for me.
So are there any ideas? Nothing in this thread seemed to work for me, I can't select "this isn't me" and rebooting doesn't magic it away. I'm at the point where I would just reinstall the OS but I of course have no disc for windows 10 and have lost my serial for 7, which I upgraded from months ago.