Your 1998 Pontiac Bonneville will not start but the security light and the seat belt light stays on what could this be your mechanic has had your car three weeks now?

Are you using a copy key, or the original, the original should have a chip in it to unlock the security, if not a chipped key, the security system will not unlock, Key will have a little black square on one side. Will neeed to have vin# and info to get code from GM to cut new key and program the chip.