[SOLVED] No preview only of Excel files in Explorer, Office 201x

Like many I had this problem that suddenly since several months my Excel spreadsheets would suddenly not show in Explorer preview and instead I received in the preview an error message "this file can't be shown in preview". All probably happened after some of the many updates.

I tried everything from registry keys to office repair to running the icacls string.
No go, nothing worked in matters Excel files but everything was correct.

In PC settings under >"apps" selecting >"default apps"
Scroll all the way down there are three menus:
- choose default apps by file type
- choose default apps by protocol
- set defaults by app


Select menu "set defaults by app".
There are all major apps, but not all are listed.
Click on Excel and up comes a button "manage".


Therein is a list "file type and protocol associations".
Scroll down to last entry at the bottom of all. XL.. file types
And look for the entry "MS – Excel Url:Excel Protocol"


it is likely unchecked and offers "choose an app".

Click on it and you get options aside from looking in the Microsoft store: Excel and perhaps another app.
Select "Excel"

Thereafter check your Excel files preview in Explorer.
🎺🎺 Drumroll.... 🥁🥁
Preview for all Excel files in Explorer works again! Snappy and fast! 😀😁🕺

The likely culprit was once again a Windows "update" which resets for unknown reasons some settings. This happens notoriously whenever there are cumulative updates, e.g. certain group settings which notoriously appeared reset. For example "do not include drivers with Windows updates".

So remember this, this is apparently where the culprit lies after you have tried like me everything else!
(I only spent about cumulative over 13 hours in the last several months trying to resolve this issue...)

Amendment (05/07/21):
Last few days it disappeared again. I also learned that Excel must run as "by-stand" in the background.
Culprit found in privacy settings under "PC settings".
Under "Privacy" > "Apps Permissions" "Background Apps" apparently you need to have let apps run in the background "on" body can turn all listed apps off you must have "Office" on "on".

I'll update that after a few reboots to see if it holds up

Last few days Excel file preview in Explorer it disappeared again.
"This file cannot be previewed".

I also learned that Excel unlike Word et al must run as "by-stand" in the background.
Culprit setting found in privacy settings under "PC settings".
(Watch out as any third party privacy modification app for Windows 10 can create that havoc)

Under "Privacy" > "Apps Permissions" "Background Apps" apparently you need to have "Let apps run in the background" on "on" but you can turn all listed apps off except you must have "Office" on "on".

I'll update that after a few reboots to see if it holds up!





Well it worked for a while and started again with the same problem...
I spent an absurd amount of time searching for answers on the Internet only to get a constant repetition of same and silly suggestions. So I posted again: The notorious "No preview only of Excel files in Explorer"