Check for updates

1.      Press Windows logo  key + R, type ms-settings:, and then select OK. This opens Settings.

2.      In Settings, choose Update & security  > Windows Update , and then select Check for updates. Install any available updates and restart your PC if required.

Restart your device

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.

Try the troubleshooter

For assisted support, try the Start menu troubleshooter. After you've completed the troubleshooter, restart your device.

Create a new local administrator account

If you still can’t open the Start menu or Cortana, try creating a new local administrator account to see whether you can open the Start menu using that account.

If you're signed in with your Microsoft account, remove the link to that account first by doing the following (otherwise see "Create the new administrator account"):

1.      Press Windows logo key Windows logo  key + R, type ms-settings:, and then select OK. This opens Settings.

2.      Select Accounts  > Sign in with a local account instead.

3.      Type your Microsoft account password and select Next.

4.      Choose a new account name, password, and password hint, and then select Finish and sign out. 

Create the new administrator account: 

1.      Press Windows logo  key + R, type ms-settings:, and then select OK.

2.      Select Accounts  > Family & other people  (or Other people , if you’re using Windows 10 Enterprise).

3.      Under Other people , select Add someone else to this PC.

4.      On Windows 10 Home and Windows 10 Professional, provide a name for the user and a password, and then select Next. On Windows 10 Enterprise, select I don’t have this person’s sign-in information, and then select Add a user without a Microsoft account.

5.      Set a user name, password, and password hint. Then select Next > Finish.

Next, make the new account an administrator account.

1.      Under Family & other people  (or Other people , if you're using Windows 10 Enterprise), choose the account you created, and then select Change account type.

2.      Under Account type, select Administrator > OK.

Sign out of your account and then sign in to your new account. If you can open Cortana or the Start menu, move your personal data and files to the new account.

If the problem still isn't fixed, try deleting the old administrator account:

1.      Under Other users, select the old administrator account, then Remove > Delete account and data.

2.      After the old account is removed, restart your device and sign in with the new account again.

If you were using a Microsoft account to sign in before, associate the Microsoft account with the new administrator account. In Settings  > Accounts , select Sign in with a Microsoft account insteadand enter your account info. 

Reset your PC

If none of the previous options work, try resetting your PC using Windows 10 recovery options.