To track your progress and get a certificate, you need to be logged in with the email address you used to register for the course. If you are not logged in, or are logged in with a different email address, your progress will not be tracked.
You can still access all of the course modules if you are not logged in, so if you want to take the course just for your own skill development, you don’t need to register or log in. However if you want to receive a certificate, you need to do all the modules while you are logged in.
