Microsoft Store and various apps don't work in Windows 10 version 1903

'Maybe try it with the cumulative KB4512941 too'

Again?  Do you really think that reverting from the present non-working situation to the pre-updated non-working situation described in the original posting will fix the Store?

'BTW, my version of Calculator is higher than yours...'

I looked at one of my other PCs where the Store and Store Apps are working properly.  On that PC, Calculator has the same version as yours.  So I guess that on the failing PC, besides the Store and Store Apps not working, they also don't get updated by Windows Update.

'Maybe set your default language to English (instead of Martian) at "START, Settings, Time & Language, Language".'

In Windows NT 4, Service Pack 4 updated the True Type Collection of Martian Gothic to have 3 fonts instead of 2.  The Gothic font completely broke in Word 97 and Word 98, but oddly not in Wordpad and not in Excel 97.  In Windows NT 5 Beta 2 (before it was renamed Windows 2000), the Your Anus language version had the same breakage as the Martian language version.  But when Windows 2000 was released, the Your Anus version had Martian Gothic working correctly, while the Martian version still broke Martian Gothic.

In Windows XP Martian language version, when a Martian user set her Windows account name to her actual name in the Martian language, some Windows APIs that were supposed to return her user name only returned half of her user name.

In Windows XP Martian language version, when a DLL was located in a folder whose pathname had components named in Martian, the regsvr32 command broke.

In Visual Studio 2005 Martian language version, when a Martian user set his Windows account name to his actual name in the Martian language, the Visual Studio toolset for Windows CE targets couldn't compile C++ programs.  I don't remember if Visual Studio worked when targeting ordinary Windows systems.

From Windows 2000 until Windows 8.1, when a PC had a Martian USB keyboard, the Martian language versions of Windows insisted on pretending the keyboard had a Your Anus - Yankland (not England) layout instead of Martian - Mars layout.  For Windows 2000 and maybe XP, Microsoft provided a downloadable Fixit, but for Windows 8 I had to use regedit, and I don't remember what happened with intermediate versions.  But then the War of the Worlds took place, a Martian hacked into Microsoft, and Windows 10 Martian language version handles Martian keyboards correctly.

So yes, I'm well aware that Microsoft doesn't test its Martian language software.  Some Martians, and some of us aliens who used to live in Mars, wished that Microsoft would have been prohibited from selling its products there.

However, the Martian store is working on my other Martian PCs, just not this one.  So your racism isn't the answer.

I don't know how I got back into this thread. I'm sure I was in a similar one, but didn't think I was here. Absolutely - no - don't do everything all over again. I thought I was somewhere else giving that advise. Thanks for reminding me of that movie, though. It was a funny one - "Mars Attacks". They conquered Uranus before they got here, IIRC.

Sadly, I think you are  right, as you edited into your original post...

"It doesn't look like this problem is going to get solved.  It looks like the Windows installation has to be scrapped and a new clean install from scratch has to be done, followed by reinstalling all applications and repeating all settings of all applications etc."

And remember what Greg said: "You're overdue for a Clean Install."

And I say remember to make a Windows system image backup afterwards to lock in the goodness. I think that's in Greg's post too. Make one immediately after the drivers are right in the clean install & that much works well. Then, you can always return to it, if things go bad along the way of installing all your apps & recovering your files. Then make another backup when all is well with the installations.

Now I'm off to Pluto. I think the thread I was in is on there. Good luck, & keep us informed.

Edit: Some settings can be handled by syncing them before the clean install. Then afterwards they automatically will be retrieved when logging into the same Microsoft account...

https://www.bing.com/search?q=how+do+i+sync+my+settings+in+windows+10%3f&filters=guid:%224026102-en-dia%22%20lang:%22en%22&form=S00028

how do i sync my settings in windows 10?

That link is at "START, Settings, Accounts, Sync your settings".

With the upgrade to Windows 10 version 1909, Calculator started working.  The first time, the Search icon next to the Start button still displays @pathnames instead of human readable labels, as shown in the screenshot posted September 2, 2019.  However, the app opened.  Interestingly, the second time I invoked the Calculator, the Search icon displayed correct labels.

However, some other apps such as Microsoft Store itself and Photos still don't work.

I've upgraded to 1909 too. We were able to do so (through Windows Update) because we already were 1903...

https://blogs.windows.com/windowsexperience/2019/11/12/how-to-get-the-windows-10-november-2019-update/#pGHQpKkVHHy7QEhj.97

How to get the Windows 10 November 2019 Update

I believe the download site will say "November" (instead of May) when 1909 is available...

https://www.microsoft.com/en-us/software-download/windows10

Download Windows 10 - Still says "MAY" this very minute

As soon as available, make 1909 Installation media & try another in-place upgrade with it. If that fails, I think a clean install is the only cure.

Photos & the Store both continue to work for me. Here is what typing Calculator into Search produces...

Hello,

Try to re-register apps. Perform these steps:

1. Search for Windows PowerShell using Cortana or Windows Search.
2. From results, right click on Windows PowerShell and select Run as administrator.
3. Then type following command and press Enter key:

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

Let the command complete.

4. Close Windows PowerShell and see if the issue is resolved now.

If issue still persists, we can try creating a new user account from User Accounts window. Press Windows + R, type netplwiz command, click OK. In the User Accounts window, click Add and create new account. 

In case if nothing helps, we can perform repair upgrade:

https://www.kapilarya.com/how-to-repair-windows-10-using-in-place-upgrade

Hope this helps! 

Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.