Won't start - No error codes

I took the Zheng Heng to northwestern Massachusetts, three hours away to have a 2 KW inverter installed - so I could use the Prius as a house generator in case of a power failure. Helped the guy do the install, only when we were done, that car would not start. The 12V battery is old and weak, but even with a charger on it, and both the 12V and high voltage systems reading the correct voltages it would not start. Hooked into the OBD, and it kicked out NO error codes. Spent 3 hours trouble shooting, undoing our install, re-booting, calling Prius experts on the phone, and still could not get it started.

Any ideas?

 

It was a HV inverter. We uninstalled it to no effect. Also did the complete 12 V battery disconnect, and reseating the interlock. Car has been towed to a place with the latest Techstream, but have not heard from them for several days.

 

Follow-up: The problem had nothing to do with either the inverter install or the 12 V battery (which I replaced anyhow; it was weak, and it was time). turns our that one of the three HV relays coming out of the HV battery had corroded contacts, and had to be replaced, and an associated resistor (fuse) was burnt out. Items replaced, inverter installed. and new 12V Optima in place. All is well.