dash lights on with repeated hissing noise

Yesterday afternoon I got my car back from the dealership (dash lights still on).
I tested for power at accumulator assy plug--it was present at the proper times, but the motor did not activate.
In the mail, I received the latest used accumulator assy this afternoon, and did the swapping again.
FWIW, I was able to "set aside" the inverter without draining any of the coolant.
I put most everything back together, fired it up, and heard the motor pumping every time I depressed the brake pedal.
I presume that the dash lights will stay on until the brakes are properly bled, and the codes cleared.
Getting closer. More to follow...

 

Success!
Technician said that everything went smoothly, and all is good.
Thanks to all for for your inputs--much appreciated.

 

Yep, after the initial replacement of a "guarenteed to work" used part, you (I) proceed under the belief that the used part in fact does work properly. It takes a while to admit to yourself that the used part is defective.
On the flip side, I learned quite a bit about some of the Prius systems. It was interesting to remove the accumulator motor from the assy to see how it functions, as well as how to bench test the accumulator motor.
All in all, I'm grateful that it's now working as it should.