I was having difficulty with Windows 10, the start menu was “sticky” it would need a few clicks to bring up the menu, also Cortana would not work when clicked on and when typing in the start menu.
I found a working solution here:
Click on task manager
Then in the task manager menu click file>run new task
Check create task with admin privileges and type powershell then click ok
Type sfc /scannow
Wait a few minutes for the scanner to check and hopefully repair the windows files.
The next step may have been unnecessary but I did it anyway
Still in powershell after the scan has completed create a new account new user username password /add
Once created restart and login to the new account, after the initial setup for the new user I found that the start and cortana were working fine.