KillaHaddy 

For those who have been trying to fix their taskbar and start-menu not working problem and trying the command [Get-AppXPackage ......] and it is not working for them then try the following procedure, i was having same issue and THIS WORKED FOR ME...!!!

I am quoting this solution from another page:

https://learn.microsoft.com/en-us/answers/questions/963295/appxmanifest-xml-location

Limitless Technology

Hello,

This may seem some corruption of the Package, please try the next:

Make sure to Run PowerShell as Administrator

1. Run PowerShell(Admin)
   Copy and paste the command below then press Enter

Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

Restart your computer

1. Run PowerShell(Admin)
   Copy and paste the commands below one at a time then press Enter

Set-ExecutionPolicy Unrestricted

Press Y

Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

Restart your computer