This happens if a website prohibits via CSP rules of otherwise via a X-FRAME-OPTIONS header in the HTTP response headers to be embedded on an other webpage like happens if you include this page on your igHome page. Google might be more forgiving in such a case and allow this or maybe it uses another link.

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options

Thank you cor-el for your response but all that information is way over my head. Is there a way that I can fix this so that I can see the Google Calendar again in my igHome window on Firefox?

This could be about third party cookie partitioning (cookie isolation) that prevents the Google Calendar page from getting the Google session ID cookies casing you to get the Google account login page.

You can try to set network.cookie.cookieBehavior = 4 to disable partitioning if this pref is currently set to 5 to see if that has effect. See "How do I know if the site breakage is caused by Total Cookie Protection?":

• https://support.mozilla.org/en-US/kb/total-cookie-protection-and-website-breakage-faq

You may have to clear existing cookies for the Google account.

You can open the about:config page via the location/address bar. If you get the warning page, you can click the "Accept the Risk and Continue" button.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

cor-el. Thank you so much for your help. I followed the instructions in the first link above and set my Total Cookie Protection to "Custom/Cross-Site Tracking Cookies" and it fixed the problem. I can now see the Google Calendar again.

Here are the instructions I followed.

Can I disable Total Cookie Protection without disabling Enhanced Tracking Protection?

Yes. To disable Total Cookie Protection follow these steps:

   Select the Custom setting under your Enhanced Tracking Protection settings.
   Set the drop-down menu next to Cookies to Cross-Site Tracking Cookies. 

This will disable Total Cookie Protection but keep Enhanced Tracking Protection enabled.