Does your cadillac have the chip in the key? Looks like the ones pictured below?
There are two fuse panels under the hood, basically both in the same location on the drivers side fender under plastic cover.
There is a third fuse panel in the trunk on the backside of the rear seat.
If the fuses all look okay, the most likely source of your problem is a broken wire coming off the igniton lock cylinder. The lock cylinder has tiny wires that carry the signal from the chip in the key to the security module. These wires often break because they flex each time the key is turned.