Python Manager MSIX does not install. Secureden?

[Poddster]

Install source and version

• Installed from the Windows Store
• Installed with the MSIX from python.org
• Installed with the MSI from python.org
• Installed with winget install 9NQ7512CXL7T

Version: 26.1.240.0

Describe the bug
It doesn't install. I click install, it gets to 98%, I then get this error:

App installation failed with error message: AppxManifest.xml(150,26): error 0x80070020: Cannot register the PythonSoftwareFoundation.PythonManager_26.1.240.0_x64__3847v3x7pw1km package because the following error was encountered while registering the windows.appExecutionAlias extension: The process cannot access the file because it is being used by another process.
. Try again and contact the package publisher if the problem persists. (0x80070020)

To Reproduce
Steps to reproduce the behavior:

1. Click install

Expected behavior
I expect it to install.

Additional context
I can't see any specific logfiles in %TEMP% that go with python manager

I work in a "secure" IT environment (using secureden), and each instance of admin elevation has to be approved by IT.
However the installer/UAC is not asking me to elevate to admin, so I'm not sure if that's the issue. I can't see a way in file explorer to run the .msix as admin, as the "right click > run as admin" option is only for .exe, and I don't fancy asking IT for a admin command prompt :)

The "windows store" is disabled by IT policy.