No power no crank

look for large fuses and fusible links near batt

Check to see if your dash has a light "pass key" (upper left side of cluster) that stays on when you try to start the car. That will indicate that either your key/lock is worn or the wire that goes to the key tumbler is broken. This is a common problem on the GM cars of this era with the resistor in the key check out these 2 videos chevy shown but same fix for buick https://www.youtube.com/watch?v=KenpMVT99rY&t=3s https://www.youtube.com/watch?v=KenpMVT99rY&t=3s Hope this works for you.