This morning the production Shibboleth Single Sign-On Service (https://login.queensu.ca) was returning error messages to users attempting to login to selected sites, including:

Lynda.com
Concur - Expense Reimbursement System
Libauth.com
smithschoolofbusiness.freshservice.com
Open Science Data Cloud
Scholar's Portal
Simply Voting
TheisabelTickets.universitytickets.com

ITS has resolved this issue, and service should be restored as of approximately 9:35am.