Accessing Instagram Individual Pages through Zscaler

I am trying to access Instagram individual pages (e.g. www.instagram.com/instagram/) through ZIA on Windows 10 (the browser is Chrome). Without logging in Instagram and trying to access the page with putting the URL into an address bar directly, I get an error message saying “Sorry, this page isn’t available.” On the other hand, after logging in Instagram, accessing the page is successful and the content is displayed. I wonder why such difference occurs. Does anyone encounter the same issue and know how to troubleshoot?

I added instagram.com to the authentication exemption list and it works for us