Windows 10 Start Menu Not Working

Before you proceed, you may want to create a system restore point first so that you can revert back if you find that the results are not what you expected. 

Tip: try restarting the computer first. Turning it off and on again is a quick way this issue can be resolved. Or you can also turn on tablet mode and turn it back off. 

You’ll need to open Powershell or Command Prompt to run these steps.

  1. To open those press Ctrl+Shift+Esc to open the Task Manager. 
  2. Click on the File menu > Run new task. 
  3. To open a command prompt window, type: cmd 
  4. To open a PowerShell prompt, type: PowerShell
  5. Remember to check the “Create this task with administrative privileges” check-box. Then hit “Enter”. 

Before you make major changes, start by running Windows updates.

  1. Right click the Taskbar > Select “Task Manager” > From the top left hand corner select “File” > Run new task 
    Enter: control update 
    Remember to check the “Create this task with administrative privileges” check-box. Then hit “Enter”. 
  2. Run an SFC Scan. To do this, open an elevated command prompt, copy-paste the following and hit Enter: sfc /scannow 
    Restart after the scan is over and see if it helped. 
  3. Repair Windows Image. Open an elevated command prompt, copy-paste the following and hit “Enter”: Dism /Online /Cleanup-Image /RestoreHealth 
    Restart after the scan is over and see if it helped. 
  4. Create a new user. To do this, open an elevated command prompt, copy-paste the following and hit “Enter”: net user /add [username] [password] 
    It should look something like this: net user /add CoolUsername Password123 
  5. Now you’ll type the following and hit Enter: net localgroup administrators [username] /add 
    It should look something like this: net localgroup administrators CooUsername /add 

Source and more info: https://operating-systems.wonderhowto.com/how-to/create-admin-user-account-using-cmd-prompt-windows-0125689/