Why can't I see thumbnails in the finder?
This just happened to me and it was fixed by relaunching Finder:
- Alt + Right Click Finder in the Dock > Relaunch
- Cmd+Alt+Esc > select Finder > Relaunch
A couple of things to try.
Remove the Finder preferences file. The system will automatically regenerate it.
- In Finder, press Shift ⇧+Command ⌘+G and enter ~/Library/Preferences.
- Then find com.apple.finder.plist and move it to the Trash.
- Right-click on the Finder icon in the dock and select Relaunch.
If this doesn't work, ensure that JPG files are associated with Preview. To do this, right-click on one of them and choose Get Info. Under the Open With section, select Preview, and then click Change All. You may need to relaunch Finder with this method too.
Any chance you have DropBox installed?
If so try this:
Go to /Users/youruser/Library/QuickLook/
and if there is a DropBoxQL.qlgenerator move it to the trash.
Then wait 5-10 seconds, and open a folder where previews weren't working.
DropBox will create a new DropBoxQL.qlgenerator when you login next (either logout/login or on restart) so if you want to prevent DropBox from screwing with your previews again then you'll need to put a dummy file in place.
In terminal run:
sudo touch ~/Library/QuickLook/DropBoxQL.qlgenerator
This will create an empty file owned by root that DropBox can't overwrite (since DropBox is running as your user when you log in).
This hasn't caused any issues I can detect on my Mac Pro (10.11.6) or MacBook Pro (10.12.2) but as always YMMV.
From this link: https://www.cnet.com/news/files-in-finder-not-showing-previews/
From the Finder's "View" menu select "Show View Options". Then select the option to "Show icon preview" and close the options window.
When a file is not associated with a specific application, it will not show as Icon.
To change that right click on one of those files and select the Get Info, in that window select the Application to use to open, and then select apply to all (Change All).
