What was your exact procedure? Yo should follow this steps:
1. Insert blank SD card in a car
2. Start the car and wait for the message "No maps found"
3. Turn off the engine and eject the card
4. Go to your computer, insert SD card in your card reader, run Tomtom Home and sign in...
5. Check for updates..navcore first, than the maps...or whatever, navcore will be downloaded anyway as a essential update within or without maps