Prestashop shopping cart empty after registration


Say, If you have a new customer added products on shopping cart, off course you need to register before you could check out, but after registration, the cart is empty.
Is there anyway that those products added on cart prior registration will retain after customer register?

1. Observed any special events while completing the registration? Such as change of the store URL. For example from the domain name without www prefix to domain with www or vice versa?
2. If none of above problem oocur, try Go to Preferences and check 'Yes' at "Cart re-display at login". As soon as the customer logs back in it will populate their cart.