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

"(1) MS Office is a big & complex thing & could be responsible for anything. Yours is 50% more so owing to the compatibility pack."

The ones I have installed are non-Store apps and they work, just like they work on several other PCs.

"If you ever do a clean install, the whole thing will be wiped & would require reinstallation."

Yes, no kidding, that (and other non-Store applications and settings) are the reason I don't want to do a clean install.

"(2) Your permissions on the Packages folder look fine. But I don't see an e-mail address in your "group or user names" box"

I do not use Microsoft accounts for my local accounts on PCs.  A few times I had to log in to Microsoft's site with Microsoft accounts in order to obtain Store apps which worked but I didn't change the method of local logins on my PCs.  I think a few of those downloaded Store apps were installed on this PC -- I have a feeling that one was one of the three versions of Dell SupportAssist which you observed and which I uninstalled.

"(a) At the Microsoft Account home page, click "Manage" under Devices..."

In fact I have done that several times, because this is supposed to be the way to transfer a digital licence when a licensed PC dies and I buy a replacement.  But Microsoft messes that up too.  For example I had a few PCs registered on Microsoft's site, but when I added one more, Microsoft forgot all about the previously registered PCs.  So if one of those PCs dies, when Microsoft is supposed to allow a licence transfer, Microsoft no longer remembers the licences it's supposed to allow for the transfer.

But this has nothing to do with the Store, as far as I can tell.  I can't open the Store on this PC so it doesn't matter if a hypothetical imaginary executing instance of the Store would be able to log in.

(1) MS Office is a big & complex thing & could be responsible for anything. Yours is 50% more so owing to the compatibility pack. But I can't recommend fooling with it much until it is actually mentioned in an error message. Then I would suggest it be repaired or reset. If that failed, next would be to un/re-install it. But let's duck any of that for now. Maybe just look through its settings to see whether any could possibly apply. If you ever do a clean install, the whole thing will be wiped & would require reinstallation. That's one of the considerations in Greg's "Clean install Windows 10" post. Be sure you have your passwords/whatever to reestablish your credentials or you lose it.

(2) Your permissions on the Packages folder look fine. But I don't see an e-mail address in your "group or user names" box (as there is in mine). I think that means there is no Microsoft Account on the computer (or maybe just that you didn't sign into it?). Does one show up at "START, Settings, Accounts"?  It would have an e-mail address under it.

But you've got to have a Microsoft Account to use the Store (Office too). So maybe you sign into it through the Store app. Anyway, can you get to it & check whether too many devices are linked to it...?...

(a) At the Microsoft Account home page, click "Manage" under Devices...

(b) Click "Sign in" on the requestor that appears.

(c) Scroll down the Devices page that opens,

     & click "Manage" under Microsoft Store device management...

(d) If you've got too many, you may unlink a device on the Microsoft Store device managementpage that opens...

I really hope that's it, but I wonder why Windows wouldn't just put up an error message instead of what's happening to you.

"Why do you have 3 of Office...?...

2007 Office System (Japanese writing) ….……....  425 MB

Microsoft Office Personal Edition 2003 ………..... 975 MB

Office .........................................................…….............…. 9.98 MB"

Compatibility pack for Office 2003 to read and write documents in Office 2007 format:

https://answers.microsoft.com/en-us/msoffice/forum/all/office-compatibility-pack/7427ece0-2682-42b3-b836-4ecb5c51a6eb

Office Personal Edition 2003 because I have around 6 licences for it.

Office installer or downloader or something that's built in to Windows 10 to persuade people to buy Office a second time.

"(1) Are you booting into your MSFT Account or at least into an Administrator Account?

(2) Is "C:\Users<your username>" native to that installation,

     or can it have been restored from a backup of a previous installation?

(3) What is at...?..."

My local account is a member of the local Administrators group.  I created the account a few years ago in Windows 7 and it has remained intact through all the Windows 10 upgrades.  But this shouldn't matter.  Missing subdirectories of C:\Windows wouldn't belong to a user's account if they existed.

SYSTEM, myself, and Administrators all have full permissions on my Packages folder, but this doesn't help when C:\Windows is missing some subdirectories needed for Store applications.

OK. I never hated Dell (& still don't). DELL continues to support mine with driver & BIOS updates. Support Assist was cumbersome to use & duplicative. You shouldn't miss it. That's right, it did do hardware tests, but those are available in BIOS & at the site too. Good that you passed yours. The other two apps I leave to you to understand. If ever you do a clean install, chances are they will be gone. Then you will know for sure whether you must have them back, either from your site or by restoring a system image. That is why I did my own clean install twice - first into a dual boot to see how the Dell would like it. It did, so I redid the clean install wiping all away to get the partitions right.

Why do you have 3 of Office...?...

2007 Office System (Japanese writing) ….……....  425 MB

Microsoft Office Personal Edition 2003 ………..... 975 MB

Office .........................................................…….............…. 9.98 MB

Regarding permissions...

(1) Are you booting into your MSFT Account or at least into an Administrator Account?

(2) Is "C:\Users<your username>" native to that installation,

     or can it have been restored from a backup of a previous installation?

(3) What is at...?...

(a) Open File Explorer to "C:\Users<your username>\AppData\Local\Packages".

(b) Right-click "Packages" in the left pane, & select "Properties".

(c) At the Security tab, does it look like mine?

I blotted out my e-mail address. Blot yours out too, if you post it. All three of those "group or user names" (click each one in turn) have the same full permissions. Only "Special permissions" is unchecked (scroll to see it).

I also wonder why there were 3 versions of Dell SupportAssist.  That didn't happen on my other PCs.  I uninstalled all 3 of them.  I had occasionally used SupportAssist to test hardware components but tests always passed.

Dell ControlVault provides a driver for some security related components including fingerprint swipe sensor.  I've never had trouble with that driver.  (Also there's a firmware update for the hardware components, which I applied years ago.)

Dell System Manager seems to assist network administrators in managing lots of PCs from an administrative application running on one computer.  I've never used it but it never hurt anything.

Again, these are not Store applications so they work.