Hi Sean, 

Welcome to Box Community and glad to assist! 

Can you have the user to follow the troubleshooting steps below. 

• Updating your browser to the latest version
• Clearing your browser's cache
• 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. 
• Restart your machine. 

Hope it works!