The following are some things you can try if you're having problems with the Start menu or Cortana. First, check for updates:
Press Windows logo key + R, type ms-settings:, and then select OK. This opens Settings.
In Settings, choose Update & security > WindowsUpdate, and then select Check for updates. Install any available updates and restart your PC if required
If you didn’t have any updates that required a restart, it’s still a good idea to restart your device to make sure any pending updates are installed.