ClassLink allows admins to make a copy of applications and distribute the copy to ClassLink users. If your district has a practice of making copies of your ClassLink apps, please note that the copy will not receive updates if changes are made to the SSO configuration.
If you run into an issue where SSO is unavailable to users from a copied app, first try removing the copied app and recopying from the original app.
The following instructions will help navigate how to remove the old OAuth app for SchooLinks and add a fresh version from the app library within the Management Console.
Navigate to the Management Console in the ClassLink Launchpad

Navigate to Single Sign-On > OAuth2 Resource Management

Within the list of Apps, Click Remove next to the SchooLinks copy that you are using

Click the Add Button and Search for SchooLinks

Click the Add button for SchooLinks Prod OAuth

Make sure your users or test users are assigned the SchooLinks App and test an SSO Log in from ClassLink.