key to cadalliac diville wont go into ingintion

It could be an anti theft function. Lock the car from outside and then wait a moment and try again. See if your steering was under tension. Try leaning into turning it one way and turning the key. Then the other way.The brake pedal circuits in the late 90's actuate a release you can hear, or they may need a fuse replaced. Try to apply the brake, then turn against the wheel, turn the key, pull gearshift down a click, retry. Get it unlocked that way, pull down into neutral, and start in neutral. please try , then report findings. A GM car doing this, may be parked on an incline and an uneven surface. With normal wear, it may take some coaxing. to get the forces acting against it relaxed.