UPDATE (13 Jan 2016)
We have received reports in the comments that this fix is failing for some users and resulting in the need to reinstall Windows 10. Please be aware of this and make sure you have your system backed up and that a new System Restore spot is saved just prior to trying this tip.
Thanks.
Original article continues...
In Windows 10, just like its predecessor Windows 8/8.1, statuses from different apps can be displayed on the Lock Screen. This feature allows you to quickly glance at the Lock Screen and see notifications relating to received emails, calendar events, the weather and other items as you are logging in. A type of heads up on where you might want to go when you first log into the OS.
There has been an issue for some users after installing Windows 10 where not all apps appear as options in the Settings>Personalization>Lock screen settings page. These apps have also been found to not display the correct icon on the Taskbar such as the new Windows Store or Mail app icons.
This occurs because an app is not fully registered on the system upon installation but there is a straight forward fix using PowerShell.
Just open a PowerShell prompt as an Administrator. You can easily do this by searching for PowerShell from the Start Menu (1), Right Clicking on the top search result (2) and then clicking/Tapping on Run as administrator. Be sure to answer yes on the User Account Control (UAC) dialog that follows.
That will open up an elevated PowerShell prompt.
Now paste this PowerShell command into the PowerShell prompt:
Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}
Before pressing the Enter key to execute the command be sure any Store apps are closed. Once the command executes you should see this happening on screen:
Once it is done you might see some red text indicating an error occurred. I have had that happen on two systems but it did not effect the fix for apps showing up in the Lock Screen Display Status options.
If you leave any apps open that can also result in an error because changes can not be made to an open app.
Once you have completed this command you can close the PowerShell prompt and all of the apps that can show a status on the Lock Screen should now be an option in the Settings>Personalization>Lock screen settings page. The correct app icon should also now be displayed on the Taskbar for that app if it is pinned there.
Thanks to @databaseJase who sent me these instructions on Twitter. They were originally posted by Gabe Aul on the Microsoft Answers forums to address an issue with apps not starting or being stuck on their splash screen.
