I got the demo and its really cool, I played to the part where you had to make the shield generator but I built it wrong and all of my crew died due to lack of oxygen, I've tried restarting the demo and every time before I finish the refining "mission" my meeple die from low oxygen, how do I fix this

on the demo you might be experiencing an issue with persistent data from the previous game. I'd try restarting the game and firing up the tutorial again.