1998 Pontiac Grand Prix no start

. Went to start my car and there was no power, tried to jump it and still no power, wouldn't take a boost. Noticed gas gauge was acting up, dim lights in the car and on the dash, when in the on position, ignition switch stuck a couple of times on that day when it went dead. Hooked up the obd II sensor and it reads a not supported error, not reading the computer, what could it be, i'm thinking the ignition switch first and then possibly the computer?Checked all the fuses, inside and outside of the car, all fine. It's a 1998 3.1 litre grand prix, 237, ooo kms, battery reads 12.6 volts. Car ran fine that whole day and went to use it again and totally dead. Checked it again today and same thing, when the key is in it sometimes rings the door chime, when put into the on position all power cuts out, obd II shuts down as well. Turned the headlights on and nothing with or without the key in the on position.I heard some clicking in behind the glove box, saw 2 resitors there, one black one grey, they seem to click when I flip the headlights on, wether or not that means anything. Thx for reading"