I tried to update my device and got a message "Your current SatNav is incompatible with TomTom's latest map update." I got an email with "Upgrade Offer: HUGE LOYALTY DISCOUNT!" I clicked on "Shop Now" and was directed to a page with discounted GO520's and GO620's. When I selected a device, the shopping cart said "The voucher code you entered is not valid or has expired." How do I get the quoted price?