Assets (or shelf) previews are empty

This issue can be caused by other software, see: Software conflicts.

If it is impossible to determine which software updating/uninstalling, look for an environment variable named "QT_PLUGIN_PATH" and remove it.

On Windows: 

  1. Open System in Control Panel. 
  2. On the Advanced tab, click Environment Variables
  3. Look for the variable named "QT_PLUGIN_PATH"
  4. Remove it
  5. Restart your computer