Car was not used so battery died. Bought a new battery and replaced it. All the lights work, but car will not turn over. Dash reads "Theft system problem car may not restart." Called Cadillac support and they said I should disconnect the battery make sure everything inside is shut off and then reconnect the battery. I did it but nothing changed. I do not know what to do and am not a car expert by any means. Can someone please help?