Thanks for sharing the screenshot and application version.
We see that you have enabled the PDF Thumbnail preview within Acrobat's preferences setting. Just want to confirm that after selecting the checkbox "Enable PDF Thumbnail previews in Windows Explorer," did you press the OK button in the lower right corner of the preferences window?
Once you do that, a configuration window appears, as shown in the screenshot below:
If you haven't seen this window, the process was incomplete. Try the steps once again.
Once done, Go to Windows Explorer> click on View on the menubar at top> change it to Large icon or Medium. It might take a few seconds to apply the changes.
Still didn't work? Open Acrobat>help> run "Repair Installation"> Close and reopen application.You may also check for pending Windows updates [if any]
I enabled the tickmark in the checkbox before making the post. I kept facing the same issue. My windows OS is up to date. I went to Windows Explorer> View on the menubar at top> changed it to Large icon or Medium already before making the original post.
After your suggestion, I repaired the installation as per your steps. Still facing the same issue. I also rebooted my laptop.