How to reset the Windows Push Notification Platform?

For my user account, the Windows Push Notification Platform seems to be messed up. I have the following symptoms:

• In the Settings charm, Notifications is grayed out. The tool-tip is Turned off by Group Policy.

• Visual Studio fails to install an app that is capable of toasts and live tiles with the following error:

  Error 1 Error : DEP0700 : Registration of the app failed. error 0x80072EE4: The Visual Elements extension failed while processing the Notification element. (0x80073cf6) MenSaar

  The event log Microsoft/Windows/Microsoft-Windows-AppXDeploymentServer/Operational contains many related entries, the most relevant of which appears to be the following:

  error 0x80073CF6: AppX Deployment operation failed. The specific error text for this failure is: error 0x80072EE4: The Visual Elements extension failed while processing the Notification element.

• The same app fails to install from the Windows Store.

• The event log Microsoft/Windows/PushNotifications-Platform/Operational contains many of the following entries:

  The Windows Push Notification Platform has encountered an error in file: base\diagnosis\platform\notifications\platform\endpoint\platform.cpp, function NotificationPlatform::Initialize, line 595: 0x80072EE4.

  The Windows Push Notification Platform has encountered an error in file: base\diagnosis\platform\notifications\platform\ui\cachemanager.cpp, function CacheManager::Initialize, line 170: 0x80072EE4.

• The event log Microsoft/Windows/Microsoft-Windows-TWinUI/Operational contains many of the following entries:

  The Windows Notification platform has failed initialization. Notifications will not work until after a restart.

• My Notifications settings are in the following state:

  

  Usually, this is impossible: The latter options are only grayed out if the first option is disabled. I can un-gray the latter options by disabling and re-enabling the first option, but this does not persist.

These issues are local to my account (at least the first one, I haven't carefully tested all of them).

By resetting that part to the profile to the default profile, I verified that ~\AppData\Local\ is not the (only) cause of the problem.

Windows logs this error to HKCU\Software\Microsoft\Windows\CurrentVersion\ImmersiveShell\TileNotifications\. While writing the registry entry, explorer.exe has the following stack:

How can I reset the Windows Push Notification Platform? What else could I do to remedy this?

The hard way: Surrender your profile.

Copy your profile to a safe place, delete & re-create your account, log in once, copy back all data except for the Microsoft folders in AppData\Local and AppData\Roaming and the Registry. Only copy back the remaining stuff on a one-by-one basis, carefully checking whether you broke something and rolling back in case you did.

This solved the problem for me for now, but for future reference, I'm still looking for an answer.