Hi Fran, 

Welcome to Box Community and glad to assist! 

To correctly preview your Box files, please check the following, 

• Updating your browser to the latest version


• Clearing your browser's cache


• Make sure you're using the most recent major releases of the following web browsers and desktop/mobile operating systems (OS). 


• Using Box with an alternate browser, computer, or network. 


• Temporarily disabling any internet security/firewall programs to test whether they conflict with Box (Note: you may need clearance or assistance from your organization’s IT department/helpdesk to do this)


• Temporarily disabling any plugins/extensions in your browser


• Removing unwanted extensions, plug-ins, ads, pop-ups & malware:
  
  • 
    Chrome, Edge, Firefox, Safari
    
  
  


• Restart your machine

Hope it helps!