Gee thanks Microsoft!
I downloaded a different calculator app, but really, calc failing?! How basic is that?!
Wait till it happens to Windows Store
Then you poked. Have had to re-image 2 that died during online app updates.
Windows Store doesn't work either. I click it, nothing happens. Fortunately I've never needed it.
I thought W10 might be the version that didn't need the occasional re-install, but seems I'm wrong. Maybe when the next big update comes out it'll fix itself.
I've had this a few times and had to re-register the store again with this command I think.
powershell -ExecutionPolicy Unrestricted Add-AppxPackage -DisableDevelopmentMode -Register $Env:SystemRoot\WinStore\AppxManifest.xml