Sign in first. It takes you straight to the class that needs cover, and after that cover links open without signing in.
That sign-in link doesn't work any more. Sign in with your email, or ask a manager for a new link.
We need an email address for you before you can sign in on a new device. Ask an owner to add it on the People page.
You're in the app on your home screen. It signs in separately from your browser, so sign in here once.
Tap the link in your message. It signs you straight in.