You're seeing this message because there was an issue authenticating for the service you wish to access. Most likely, you are using a bookmark or link that goes directly to the shibboleth authentication page (shibboleth2.uchicago.edu). This will not work. You should make sure you are going directly to the web page for the service you wish to access, such as my.uchicago.edu or classes.uchicago.edu; if you are going to the correct page, it will then bounce you to the shibboleth authentication page and you should be able to access that normally.
The University of Chicago relies on a service called Shibboleth to provide login authentication to University and external web services.
Shibboleth allows users with a valid CNetID to access multiple web applications with a single sign-on. Once a user logs in to one resource, they are granted access to multiple web applications, for which they have appropriate permissions, without being prompted to log in at each. When Shibboleth is utilized to control access to external web services, the system will evaluate the user's credentials and determine if access may be granted to the secure site. Whether or not the user may be granted access to secure external services with their CNetID depends on their affiliation with the University, various permissions associated with their account, and the requirements of the external service.
Alumni account holders may contact firstname.lastname@example.org or call 1-877-292-3945 between 9 AM and 3 PM CST with any questions.