This is because the email you are using in attempting to login is not part of the list of account approved for access. You could be authenticated by google or even have a valid CU email, but as long as your email has not been uploaded to the platform by the support team, you might keep getting this error. Contact the HR Department for support

Since google powers the organization's emailing systen and every member of the institution is automatically assigned an account, Gmail handles the authentication process while this platform handles authorization. Google caches your details from your previous successful login into a cookie file for some period of duration. That cookie file is what is sent to the server for authentication. A quick solution is to use another browser or open this website on Incognito mode. Although challenges of this nature are less likely to occur in most user cases