Strange Set if Codes on 2009 Prius

Somehow it started after a few days (without disconnecting the 12v source?), yet now it won't, and you tried(?) disconnecting the 12v source for a few minutes and that didn't allow the vehicle to start again?

Try disconnecting the 12v battery for a couple of mins, then reconnect and attempt to start the vehicle. After reconnecting the 12v source it will take two (2) power cycles to make the vehicle ready. If it starts (let it run for a couple of minutes to charge the HV battery some), then turn it off, and if it doesn't start a 2nd time, you likely have a HV isolation fault, aka P3009 / P0AA6.

You can test if your obd2 scanner App is working (what is the name of the App again?), remove the orange disconnect (service plug) on the drivers side of the HV battery, then scan the ECUs for DTCs and post them here.

That valve does very little except warm the engine with stored hot coolant on start up. Though it is an issue, and can be fixed as well.

True. Not sure who suggested the LX scanner, though it may work with Dr Prius (phone app) or Hybrid Assistant (phone app).

Have you thought about trying other OBD2 software with your OBD2 adapter?