Car won't start turn switch it lights up but won't start

doesn't turn over ( crank ) ? or won't start ( run ) when it does ?

If you're saying it won't crank, try starting it in neutral. If it starts in neutral it's the neutral safety switch. If not, get a hammer and hit the starter a few times. If that gets you going it's a bad starter. Your Buick has GMs VATS security system. The chip on the ignition key must contact two tiny wires inside of the ignition lock cylinder so the computer knows you're using the correct ignition key. Those wires break off over time and lose contact with the chip on the ignition key. The computer will think you're trying to start the engine without a key. So it will not allow the starter to crank. You need to check the resistance value of the chip on the ignition key and compare it to the chart below to determine which VATS key you have. Then you need to unplug the two wires under the dash that come from the lock cylinder and check the resistance value across the two wires with the key in the ignition. You should rotate the lock through all the positions to make sure you don't have an intermittent problem. The resistance value on the two wires should match the resistance value of the chip on the key exactly. If not you need to replace the ignition lock cylinder. The new lock will come with a template for cutting the new VATS keys. The template will NOT start the engine. You need to use the chart below to determine which key you have and get that number key blank then use the template to cut the VATS key blanks. Hope that helps! Jim