Some users of win10 reported that they found a key error after starting up: the start menu and Cortana can't work. They said they would solve it after logging out and logging in again, but it's useless to restart several times. Don't worry when you encounter such a problem. Take a quick look at the following tutorials, which may be helpful to you!
Restart the computer first
Then click "control panel" to open the interface.
In the "control panel" interface, click "view method" and select "small icon"
Find the "management tool" and left click to enter.
Find "service" in the management tool and double-click to open it.
In the service menu, find "user manager" and double-click to open it.
Find the startup type and set it to automatic
Click "apply" at the bottom right, and then click "OK".
Finally, restart the computer.
Press Ctrl + Alt + delete and select to enter the task manager.
Switch to the service page, select any service, right-click and select "open service".
Find the user manager, select it, right-click and open the properties.
Select automatic in the startup type.
Click OK again. Then log off the computer or restart it.