After replacing the 12 volt battery, hatchback door still won't open, however I drove the car several miles, only it lost power, the red triangle light cut back on, along with HV battery fans. Display also showed that symbol on the energy light, which went from green to red, with the picture of a broken car, or so it appears to me. Is it the 12 volt battery that is bad, although brand new from NAPA, or something more serious? Thanks a bunch!
The battery is probably not the problem... it sounds like the 12V battery charging device (the actual name is DC Converter/Inverter-- it's what priuses are using instead of alternators) is the problem. You can have the guys at most auto parts stores check your alternator (for free), and I would expect the test to be the about the same for whatever you use to charge a 12v battery. You basically need about 14 volts for charging a 12 volt battery.
Of course, most autopart stores also have diagnosatic code readers, so that might be helpful to diagnose the electrical problem.
Note: the size of the battery is important. Look in the owners manual to see what exact RC rating that your 12v battery is... if your new battery is the wrong size that might explain the warning light.
Regarding the door issue, I would look for problems with the door, not the battery. While I'm not very familiar with prius(es?), I've never heard of a car battery causing a problem with a car door opening... the battery in the key fob could cause a problem.