title: Image preview / thumb not showing in Drupal 8
body: <p>I am facing a strange issue regarding image preview in Drupal 8. I tried will all the patches available in the net
  -disable "itok"
  -set permission 775 to sites/default/files/styles directory and subdirectory
  -even changed the default file permission from 0664 to 0775
  -disable Options in .htaccess file
  None is working</p>
  
  <p>The image below is a preview page by "focal point" module. You see the preview is not showing. But if i click on preview, the image is showing at the bottom. I checked in the corresponding folder all preview images are there. A sample url is like this:</p>
  
  <p><code>/sites/default/files/styles/facebook/public/assets/Q292ZXIyMDExLTA2LTIzIDE5OjE2OjI3.jpg</code></p>
  
  <p>Now if I go directly to that image in browser, its displaying correctly. And after that, if I refresh the focal point preview, now that image will display. But if I clear the varnish cache, everything will be as before.</p>
  
  <p>In whole site, where there is image preview, after upload or any preview, its happening the same.</p>
  
  <p>The system is based on Drupal 8.4.x
  - Its in Acquia Hosting
  - Its using Media Entity, Media Entity Image, Entity Browser, Crop modules etc</p>
  
  <p>I am banging my head almost two days, no clue of this issue. If anyone can help, will be highly appreciated!!</p>
  
  <p><a href="https://i.stack.imgur.com/zffgr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zffgr.png" alt="enter image description here"></a></p>