What does it mean if my account has expired?
When you register by email, a temporary account is created for you once you've entered your email address. At the same time, an email is sent to you so you can complete your account registration, you have 7 days to do this.
If you don't manage to complete your registration, your temporary account will expire in 7 days. If this happens, you'll see an 'account expired' message when you try to play On Demand content.
To resolve this, you just need to register again (and yes, you can use the same email), as if you're registering for the first time.
Just remember to complete your email registration within 7 days to avoid your account becoming expired again.