No ready light, no start

This is a big problem. The traction battery has a high voltage ground fault. You should not be able to measure voltage from either battery cable to body ground. The fact that you can measure this shows that some of the modules have leaked electrolyte which causes the ground fault to the battery case.

The car probably has at least one other issue besides the high voltage ground fault, since after the 12V battery is disconnected and reconnected, you should be able to start the Prius once if the only issue was the ground fault.

For example it is likely that at least one battery module has failed. This is evidenced by your voltage measurement not being in a multiple of ~7.2V.

The 28V measurement probably comes from four modules and is plausible. However the 33V measurement probably comes from five modules, and shows that two or three cells are dead (1.2V each). Or those modules are substantially drained compared to the other sample of four modules.

Imbalance between module pairs would be another reason for the car not to start. The traction battery ECU tracks voltage of module pairs. If the difference is greater than 0.2V the ECU will log a fault and not allow the car to start. If the battery were operated in that condition, a module may overheat and catch on fire.

Get Toyota Techstream software (Mini VCI) so that you can retrieve the diagnostic trouble codes.

 

Thanks, @Patrick Wong! I knew you'd be able to get this going in the right directions. I appreciate your knowledge and helpfulness.

 

Scanned with LAUNCH and got these codes P0aa4,P0aa1,P3030,P0a0d,P3000,C1241,C1242,C1249,C1259,C1310,C1313,C1353,C1354,C1377,C1378,B1800,B1801,B1810,B1811,B1421,B1433,B1200,B1269,B1271.l later discovered that the Switch on main relay/HV battery was swinged IN but the handle not pressed/locked down .l press down and started the car Wala! Ready came ON and engine run.l scanned while engine was running only three fault codes remains P3000,C1259 and C1310.