Password dialog box differs between Macs
If you see the old unlock screen (gray window asking for your username and password) you have to delete the following file:

/etc/cacloginconfig.plist

If you delete this file, you will see the new unlock screen (like the login screen) and touch ID will work again. 


  Summary: If "/etc/cacloginconfig.plist" exists in 10.9 +, the screensaver unlock screen will be controlled by SecurityAgent (old style). Admins, when they successfully authenticate, will be allowed to take over the user's session.  Even if "system.login.screensaver" in AuthDB is set to "use-login-window-ui", this will be overridden by the existence of "/etc/cacloginconfig.plist". We will still be presented with the SecurityAgent style login window. 


More Info: 
http://www.openradar.me/19177988