The user can log in correctly but the logout does not work. I have tried v1.8, v1.9 the latest 1.13. I have also tried https://your-tenant-name.auth0.com/v2/logout?returnTo=the-url-you-want-to-go-back-to-after-logout&client_id=client-id-of-the-application-in-your-tenant without success.
After the call to auth0.logout, the user is redirected to the local start page and auth0.isAuthenticated correctly shows as false. However, when auth0.login is called the user is taken to the callback page with the user automatically logged in. There was no prompt for the username/password.