From what I’ve read before, single log out only works when initiated by the service provider. When you click on the Logout button in the Okta dashboard, it only clears your Okta session but not your application session. A possible workaround is to modify the “Sign-out page URL” under Settings -> Customization in the admin dashboard to point to the logout path of your application but this might only work if you only have to support one application url.