Calder checks your session as you move around the app. If it cannot confirm it, you are returned to the sign-in page.
The sign-in page shows the message "We could not verify your session." You are also signed out on purpose after you change or reset your password, so the next sign-in always uses your new password.
Access can end when your account no longer has active Calder access. The sign-in page then shows that the account does not have active access. Signing in alone will not restore access.
What to do next: sign in again. If it keeps happening, reset your password from the sign-in page and make sure you sign in with the account that holds your invitation.
