I think my Prius not starting is going to be much different than the other posts here...

Power switch is left center

 

So, pin 6 of the switch should be chassis ground, which is then applied to pins 5 and 7 when switch is pressed (pin 14/37 of the Power Source ECU). This ground (identification point IH) is at the Cowl Side Panel Left Hand. Here is a photo of it's location. Hopefully this info helps. Could also be an issue with the ECU/ECU plug I suppose. Electrical problems can suck sometimes..and don't forget, the shaded squares in the above diagram are junction blocks.

 

Love it.

 

Have you checked your fuses? The symptoms certainly could occur if a fuse that powers up the main ECU, or other important electronics is blown.

 

Pay attention while trying to start. What does the dash do when you attempt to start? Beeping and what’s on the dash?
Put the key fob in the slot under the steering wheel try starting then. You may have hit the valet button under the steering wheel and shut off sks.

Short of that At the core of the issue is you say you have no codes that’s not possible a fail to start will launch many many codes if the immobilizer is happy with the fob.

Are a lot of lights on the dash lit up especially the red triangle of death? If not the can buss is not up and running.
First thing you must do is hook a techstream capable load code reader to the car and see what it’s complaining about. Or see if the obd is even on line reflecting dead can buss.

Amazon.com buy a VXDIAG WITH TECHSTREAM full techstream code reader $70.

 

A battery reading of 12.2V is not a great indication. for example, fully charged car battery should be reading 12.6 volts. There is a very big difference when a car battery drops even a small amount of voltage. When a car drops, for instance, from 12.6 to 12.0, there will be 75% difference.. When the engine is running, this measurement should be 13.7 to 14.7 volts. Finally, previous recommendation of replacement, is an excellent advise.

 

Actually, a Prius w/ a correct AGM battery that is FULLY charged, should have a resting SOC of 13V. Remember, AGM batteries have a higher resting voltage and require higher voltage recharge level than your standard wet/sealed batteries. If you use a 12V charger that is not AGM compatible, it will NEVER fully recharge the 12V AGM battery b/c it does not go above 13V, thus the need for an AGM compatible charger.

These were the readings of the Toyota TrueStart 12V AGM battery when I purchased, recharged, then installed:

12.94V - initial reading at home, uninstalled, and not recharged; someone probably recharged it at least once.
13.10V - after recharging for 6 hours with a smart AGM compatible AGM battery charger; surface charge giving a false high reading.
13.04V - prior to installation, after being disconnected from AGM recharger and sitting on floor for 12+ hours; surface charge likely gone, a likely true voltage reading.
12V Battery Upgrade: non-Smart Key (35A h) to Smart Key (45A h) | PriusChat
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Here's a good simple chart for AGM vs traditional battery.

Battery Open Circuit Voltage | PriusChat

 

what other lights?

 

Dash warning lights too? Which ones?

 

See if an OBD device will power up and talk to the cars system when you plug it in. If an obd device is dumb when plugged in the car's Can buss is offline.