Hi Adam, Has the car been not been used for a long time? if so could possibly be the fuel, which would need to drain the tank and put new fuel in.
But there could be other reasons, did the car sound strong when turning the key over, check the common reasons for not starting, or get a mobile mechanic just to check the car over.
Just to add if the car has not been used for a long time, could be an idea to change all the other fluids, oil, brake etc, good luck.