No error codes? Newbie needs help!

I live in Ireland. I first got a 2004 gen 2 prius used from someone on Facebook who had said there was some battery issue he just didn't want to deal with and it wouldn't run. Like it would drive a short while and shut down. He said he drove it from Dublin to Swords (40 minutes) at lower speeds and then it wouldn't run again.
I know we would have to put money into this car which is fine with me because I know the Prius will last almost forever if it's running properly. We were able to drive it a little bit about 5-10 min on the electric battery the day we got it before it just died and we had to tow it home.
My husband replaced all the battery modules twice now, new spark plugs, new 12V battery, new oil, new throttle body and sensor, cleaned out the MAF and MAF sensor, replaced the fuel pump and has cleaned out almost everything that is able to be cleaned. The HV battery is low right now but we still haven't figured out why the petrol engine won't stay running. The only code it's ever thrown is the p3190. After the fuel pump was replaced, it goes to ready mode now for a short time and the petrol engine will start for a few seconds but it sounds weak like it's just puttering and won't keep on so the battery won't charge. My husband took the lower dash apart and made sure all the sensors and connectors were plugged in properly. No codes at all. We can't figure it out. He removed the HV only button because the spring broke on it but driving on battery mode wasn't the issue. We are scratching our heads because we have tech stream and code reader but no codes are showing up. There is an error when we try to put it into drive and it says it won't charge in neutral and then pulls itself back out of ready mode and shuts the car down. We have replaced most everything and still can't figure out why the gas engine won't run. Any tips or hints or anything is greatly appreciated
Thanks, Jen

 

Reading codes with tech stream and an obd scanner. We have done all the battery load testing and all that was stable and had really good voltages. I am going through the workup now. Most of these are already done. We just cannot get the petrol engine to stay running. It's def a head scratcher. I may have to break down and just tow it to Toyota.