Car will turn on, but engine won't start

Thanks to the advice of PriusChat members, I got the 12v battery on my father's 2005 Prius working. The electrical system is active, including the security system, power locks, lights, etc. However, I've now found another problem, and I can use your help diagnosing this one.

My father's car will turn on, but instead of the ICE starting like it should, all I hear is a light clicking sound. The electric motor isn't doing anything, either, as the car won't move, and the gear shift won't do anything except shift between "park" and "neutral". I'm reasonably sure that this has nothing to do with the hybrid system, as the red triangle hasn't made an appearance and the hybrid battery seems to be holding a reasonable charge, but I can't figure it out. I've never had this issue in either of the Priuses that I've owned. Any thoughts?

 

Yes, I'm sure. Foot on the brake, press the power button, clicking. Both my brother and I made multiple attempts, and I did question whether or not he had his foot on the brake when he did it. I also know that the brake pedal was working when the brake lights came on after he tried it. As for a green "ready", I generally don't think about it because I've been driving Priuses for almost seven years, but I'll check when I'm at my family's house.

 

Does anyone else have any thoughts or suggestions?