Looking for help: this is a real stumper... my son's 08 with 250k miles completely turned off while he was parked in ready mode with the AC on. So far he has confirmed am2 fuse is good (not the inverter coolant pump). He has disconnected 12 volt battery for several minutes and then try to start after reconnection...no success. With key in slot and with key in pocket (sks). The car shows plenty of 12 volt power with headlights still bright and dome lights still bright, however to rule out the 12v battery, he had another car jump his (directly on 12v battery in rear) with no success. He checked other fuses in the engine box and couldn't find any that were blown. The brake switch still works fine. It's like the car doesn't recognize the key anymore. He hears it beeping when the fob is in the slot but no response when pushing the power button and with the foot on the brake or off the brake. The hundred amp main fuse is still intact in the main fuse box. The only lights on the dash are the key light blinking and the open door light. Clearly, there's an electrical problem somewhere. Any Ideas?
Does the small green/orange light on the power button change at all when pressing the brake to try to start? This behavior doesn't sound like very many other stories I've seen here on PriusChat, which means it might be a while before somebody (if ever) sees your thread and can speak to it. If I were in the situation, I would definitely be looking at the pushbutton start troubleshooting in the repair manual while waiting for possible answers here. Toyota Service Information and Where To Find It | PriusChat
Does the dashboard light up normally? If so perhaps you can get error codes? I'm beginning to sound like a broken record, but if the 12V is disconnected (pull the two plugs on the positive side, no tools needed), let it sit for a minute, then reconnect, will it then start? This vehicle is sometimes more computer than car, and "unplug it and plug it back in" clears any glitches which have accumulated. Do you have a second fob? Perhaps the first one was dropped and that somehow damaged it, in that case, the other fob should still work. If the RFID stops working the car will not start no matter what you do. That said, the RFID chip really shouldn't break unless maybe the fob was stepped on, or it came apart and the chip fell out.
Try replacing the AM2 fuse anyway (I would unplug the coolant pump). I have seen one case where the fuse "partially" melted, but looked intact. Otherwise, you would need a Prius capable scantool to see if any systems are online and have fault codes. Even if the car won't power on, there are 5 ecu's that can talk and give codes or data. Posted via the PriusChat mobile app.
Here's a thread that reviews several scantool apps and devices for smartphone. Some are capable of reading codes and data on all systems on a Gen2 Prius. Posted via the PriusChat mobile app.