apple watch was unlocking MacBook but not now

I'm not sure where to start looking for an answer.... RE: Unlocking MacBooks with the apple watch. After setting up my MacBook pro with the new sierra os i was pleased with the feature but then i altered the typed login password - my apple watch stopped unlocking the mac... when i realised this, i changed the password back to the original... no change? This is something i've googled the **** out of but have no fix?