Any possible life left in Hymotion L5 PCM for '08 Prius with 54k miles?

I recently bought a 2008 Prius with a Hymotion L5 PCM in the trunk. The seller's son-in-law had experienced some error codes probably 10+ yrs ago. He didn't have time to deal with it, so he restored it to stock wiring before returning it to the father-in-law. The car drives perfectly in stock wiring, with only 54k miles.

I just tried to reconnect the Hymotion to the car. But Hymotion is not drawing any current from my wall plug. Tail lights do not light when plugged in. The red dashboard light does not light in "on" mode. And the car won't even start when the Hymotion is connected. I pressed the circuit breaker button a few times also, to no effect.

What are my chances of getting the Hymotion to work again? How would I diagnose this further? I don't know how to verify if the wiring had been done correctly, but I believe the son-in-law knew what he was doing and maybe even worked at A123 systems. I found both the user and service manual PDFs online. I don't have an electrical background, but I do know software. I'm down to tinker if people tell me how, eg what tools do I need? I'm also open to hiring help (ideally in Northern California).

If anyone has ideas or knows someone might be able to help, I'd greatly appreciate it!