Green log in prompt for public files

Hi,  

I have public link access set for my files. Can you explain why the people I share it with are getting a green pop up box asking them to log in? Is there a way to disable that message for certain files? This is happening inside of a password protected web-based app at http://hellobirth.app, where we have links to our Box files. Is there a way to disable the "Log In" prompt / button, since an account is not required to access public files.