Just rebuilt the motor why will my car not start?

I do not know what the select trim means, the car is a Subaru Impreza Outback Sport Hatchback

My Dad and I replaced the head gaskets and installed a new timing belt and new idlers. We put the car back together and went to start the car. When I turn the key the fan comes on which I do not remember happening before and when I turn the key the engine seemed to fire when we put gas in the intake but would not run on its own.

In addition to this we found a three slotted wire connector under the intake manifold to the rear on the passengers side which we can not find a connection for. We do not remember disconnecting so we're just not sure if that has to do with it. I will attach a picture of this connector.