YES, the solution!!!! What more information could you possibly need? Sorry, just feeling frisky today I guess....
So, you are unplugging that wire loom and then replugging? If so, it is not "a wire", but "a group of wires". That icon at the top right is the HV battery warning icon. It means there are HV battery DTCs set by the HV battery ECU. The problem with using a generic code reader is, the Prius has 11 or more ECUs and the generic reader can read 1 ECU, the PCM. You are not therefore getting a complete picture of what is wrong with your car. JC is on the money, IMHO, you have at least a HV isolation leak which prevents you car from restarting until you do that reset by pulling that plug.
Before you go any further you need to read all your codes from all the ECUs to confirm what problem you actually have.
Y don't youvkust follow what most folks here have being saying? Get a hybrid compatible scan tool, and get the codes over here. I think that would help, instead of talking about the 12volt battery thing.
It's a brand new battery. I just replaced it days ago bc of this problem but a new 12v didn't fix the problem
Voltage leak somewhere. The Prius won't show the ready light when the 12v line is oscillating or noisy.
Best bang for buck route is an ELM 327 OBDII sensor with bluetooth or wifi and the Torque app on an Android. You can pretty much get all of the Toyota ECUs with Torque.