When you edit a page from Sitefinity, you are redirected to a public page, potentially on an entirely different multisite.
In our August 2020 code release, we added in the functionality to authenticate on domains other than www.ucdenver.edu where this bug occurs.
You can sign in on any URL that serves Sitefinity, such as the following:
If you know what URL your site is on and it's not on www.ucdenver.edu, you can go to your site's homepage, scroll to the bottom, and click the CMS Login button like you normally would.
Once you sign in and use the pencil menu to access the dashboard, you should see non-www.ucdenver.edu/Sitefinity/dashboard
Now you should be able to edit pages without experiencing this issue. If you do experience issues make sure to use this form to report the bug.
There is a different bug related to the pencil menu that will return a 404 - Page Not Found error. If you encounter this bug, visit this article to see how to remedy it.