Replaced Transmission, Car Won't Start

I am at the finishing stages of replacing the transaxle on a Prius that I picked up a few weeks ago. There was a red triangle and the previous owner told me that the code was for a bad transmission. There were toyota service records that indicated the owner before that brought the car in with issues that were diagnosed as a failing transmission.

I picked up a used transmission from a reputable auto wrecker and I think everything went in fine. I had to disconnect the traction and 12v battery, remove the inverter and remove the transmission. The "new" transmission is in and I added fluids and bled the inverter coolant.

I took the car off jack stands and when I tried to start the car... nothing. Funny thing is I am so new to these cars that I may have done something wrong. The car starts in the accessory position and that is how I bled the inverter. When I step on the brake and press power it just cycles power on and off. No action to start he car.

I am interested in any suggestions as to what might be going on. I have the 12v battery on a float charger now.

Prior to replacing the transmission, the car would start, but when I put it in drive it would stall.

I was surprised that the red triangle was still there after I connected the battery after the batteries had been disconnected for a few weeks. Do I need to clear the code?

Appreciate any and all help.

 

Yikes. That was it. After a few presses and lots of clicking the triangle is gone. The engine started after I shifted into drive. The engine seemed to run kind of rough. I noticed that prior to the new trans but thought it was related to transmission issue. I was blocked in the garage so I didn't try taking it out tonight. Will see what it does in tomorrow. Thanks!!

 

That makes sense. This car has 130k miles and the previous owner had it recently serviced and said all was working well except for the transmission issue. I thought the transmission was a safe place to start.