2007 with no dashboard when inserting key fob

I purchased a 2007 with a bad HV battery and according to the seller this was the only problem. When I went to look at the car I put a jump start battery on it and the key fob did work however it had the "Red Triangle" so I couldn't put it into Drive. I towed it home and replaced 2 bad modules on the HV battery, and after that I put the key fob in and drove it out of my garage and then back in. Well the next time that I inserted the FOB nothing! Only thing on the dash is "door open" light and "theft deterrent light" 12 Volt battery is around 12.5 volts at the battery as well as under the hood. I have checked all of the fuses under the hood and under the drivers side dash and they are Ok. The Key Fob is a little suspect because it is kinda beat up but it did work when I bought it? I can't use an OBD reader cause it says "not connected to the ECU" Any ideas would be appreciated.

 

I have a couple of code readers and the Torque app on my smart phone, So I plug the reader into the Prius and if I try to see any fault codes Torque tells me that ECU is not connected. I have a dark dash except for the door open and theft deterrent and also the main display has nothing. The original battery was a Toyota battery but I have a new Optima Yellow top in it right now. I have about 12.6 volts at the battery as well as under the hood and the jump start terminal. I have double checked the fuses under the hood and under the dash and all are Ok. I don't know if the Combination meter would cause the dash as well as the other display to not light or not? Also I have unplugged the connectors at the Positive terminal at the battery and left it disconnected for awhile before plugging it back in but that didn't help either. Would a defective ECU cause this problem?

Thanks

 

Well, guess I'm not too good at posting? I thought I replied to you question but can't see my reply. Anyway when I purchased the car it had been sitting for some time and the 12V battery was run down so nothing when inserting the key fob. I jumped the battery at the battery and then inserted the fob and the dash did light up but had the "red triangle" and would not go into the "ready" mode so I put the front wheels on a dolly and pulled it home. I repaired the High Voltage battery by replacing 2 modules that were bad and then tried starting the car, the dash did come on and I put it into D and pulled it out of the garage but only had mechanical brakes so I backed it back into the garage and shut it down, then a day or two later when I inserted the fob into the dash slot I didn't get anything and it's been that way since. So something happened I guess on it's own or maybe something I did but I don't know what it would have been. I'm thinking that something just gave out but don't have a clue to what it might be. The car had 185,000 miles on the ODO when I first saw it.

 

Headlights, turn signals, emergency blinkers etc work as well as the horn. So most all of those things work except for the dash stuff.
I can hear something running under the hood, when I push down on the brake pedal too.