Over the winter break, SAVVAS ran a major cleanup of duplicated accounts for students. Many will need to re-link their Google accounts with SAVVAS. The steps are below.
Account Linking Steps for Students

If a teacher has already removed the Realize Login item they will need to re-create it in Google Classroom for the class.  The step set for that, if needed, can be found here: https://support.savvas.com/support/s/article/Realize-How-to-access-Realize-directly-from-Google-Classroom.