Quicklook isn't working via Finder. But works with attachments in Mail messages. Whats up?

[TwitchOSX]

So, quicklook isn't working for any files that are in Finder folders. However, if I create a Mail message and drag a file in as an attachment and then quicklook that attachment, it works. Any ideas on how to fix? 10.14.6

 

[dotck]

I had issues with quicklook as well after restoring a TM backup a few days ago. No matter what I tried, only the file icon but not its contents were shown.

What I actually did is to go into /Library and remove all kinds of non-system kernel extensions, cache files and potential preference files that would have any relation to quicklook. Any applications that installed kernel extensions removed as well (VMware Fusion, Pulse Secure, etc in my case). Restarted and worked again. But can't remember exactly which files/folders I have removed. Only do that if you're aware of the risks and make sure to take backup before doing so.