newbie here with a broken 04 with no power

What's your definition of a really clean 2004? Mileage?

Do you see signs of rodent damage? Any half eaten wires or rodent feces? I don't like the fact that this car was "driving and it suddenly died". That's not a dead battery problem

Where did this rebuilt HV battery come from? Does the car have GAS in it?

 

Why are you double pushing the power button? That’s ignition only.

To start the car one push only.

 

And the dash light out is very common failure. Use search forums link up top and search

combo meter

You can get a rebuilt combo pretty cheap for $100 and then sell your core for $50.

 

What’s a forced start?

 

start: foot on brake (make sure brake lights come on) one push

did you complete the 3 step process when replacing the orange safety plug?

12v should measure at least 12.7v at the jump point under the hood, after the car has been off a few hours

 

Check the fuses in the front engine compartment, make sure AM2 fuse not blown.

you can try to turn on the headlights before starting the car, some have mentioned this method is able to turn on the dash lights if you try a few times

 

Press down on the brake pedal with a foot, then press on the start button for 2 seconds. If you've disconnected the 12v recently, then you will have to do this process 'twice', with a power down step (push/hold for 2 seconds) between the starting attempts.

If the vehicle didn't come with owner manuals, you can download them here : 2004 Toyota Prius Manuals & Warranties | Toyota Owners

Which device are you using to retrieve the OBD2 codes, as many aren't toyota hybrid compatible. Consider a mini-vci cable and techstream.

FYI : you're moderated until you've posted 5 times.

 

It’s going to be very hard to help you with all the generalized statements.

200 volts does not disappear without alot of drama. The final relay is probably not closing because your in hybrid battery alarm. If you had a dash it would probably have Red Triangle of Death RTOD and I bet you have a icon of a car in red inthe upper left corner of the mfd screen.

Bad Rebuilt hv battery is guess #1. You need a proper obd tool to pull hybrid codes like Toyota Techstream or Dr Prius phone app.

to check the hv battery using good Dc DVM with someone pushing the start button while pushing the brake down you monitor across the 2 car battery leads you connected to the relay when the battery was installed. Should have a minimum of at least 210 volts across those 2 wires. That’s the minimum voltage required to start the car. Anything lower relay will not engage. My guess is you have nothing there.
Because the hybrid battery is in alarm and relay not closing.
Hybrid battery highly monitored anything at all bad like ground fault or bad delta or low pack voltage or low current capability or a single module not good and the system will not connect it to the car. By not allowing that main
Relay to close.

or you do not have the orange hv battery safety switch installed correctly.
Push it in flip up the locking lever than that locking lever is locked by then sliding that lever straight down. Flip it up push it down.

Please be more detailed in what your posting. How you are testing it.

 

This very likely a combination of problems and misunderstandings.

1. when 12v power is lost and then restored (like replacing a dead 12v battery) place foot on brake and press the power button one time, the car will boot and just about every light on the dash will light. Keeping foot on brake, press power button one more time and those lights should reset anf the car should go ready, assuming no other problems.
2. it sounds very likely the safety disconnect isn't installed correctly at the HV battery. There are three steps, because there is an interlock contact that must be activated so the computer knows the disconnect has been installed. one-slide the safety into the socket. two-rotate the handle 90 degrees upward to fully seat the disconnect in the socket. three-push straight downward on the top of the handle and the handle will slide down about 1/2", which will activate the internal contacts to satisfy the interlock.
3. you may be experiencing the combination meter failing if you get no lights on the dash. Hundreds of threads on the forum about it.

 

That will certainly cause low bar indication.