@ClayNeal If you get the error "Invalid Credential" when trying to sync your course with Infinite Campus, you should reach out to an admin at your school or district so that they can get in contact with Canvas Support to resolve the issue. This message basically means that the login credentials that have been provided to Canvas for performing syncs to Infinite Campus are no longer valid and no syncing/grade passback will be able occur for the entire instance until the situation is resolved.
Note: It does not mean that YOUR credentials for Infinite Campus are invalid in anyway, it means that Canvas's credentials for Infinite Campus are incorrect.