Started my Computer (Windows 10 latest updates) and the Task bar did not work - no Icons or Cortana also could not use the start button.
Luckily I found a guy on an online forum that said that the problem could be Avast and that they are known for Windows 10 problems. Disabled Avast and Windows 10 started up normally. Don’t need these problems 
You could also have simply booted your computer into Safe Mode with Networking, rebooted back to regular mode and that would have solved your problem.
It’s a known Windows 10 problem.