2004 Scenic Turns over but does not start

2004 Scenic 1.9, bought car in auction, car had a flat battery at time of pick, gave it a jump start and drove 40miles home no problems.

Came home, parked up and left the car running for another 20mins so battery charges. When I came back out to turn off the engine, I noticed smoke coming from the engine bay. Turned off the engine and opened bonnet, smoke was from the coolant reservoir, I guess it over heated from being stationary.

Next morning I topped up the coolant and attempted to start the car, it started but then cut out. Tried to start the vehicle again but no luck, engine turns over fine (does not sound like a flat battery). I tried giving it a jump start from my other car no luck. Tried topping up fuel because its on a hill no luck. The immobilizer light does flash and stay on when I put int he key card but the light does go out when I press the start button. It does seem like the immobilizer because engine turns over fine. I left the battery unplugged over night to reset the immobilizer and tried this morning, but still no luck.

2004 Scenic Turns over but does not start