Can’t Figure Out The Problem

You need to subcode for that 3004 code 133 134 tech stream will be able to give you the subcode and that will narrow the process way down could be a sensor a cable do you have Frost on the nuts or corrosion on the nuts on the bus bars?. These are all possible things you replacing a cell okay how do all the bus bars and nuts look that interconnect all of these cells? You may be looking at your problem.

 

I believe the subcodes for P3004 are a 131, 132 or 133. If it's a 131, it's likely the safety disconnect is NOT installed properly.
There are 3 steps for installing. Insert into the socket, rotate lever 90 degrees upward to pull the disconnect fully into the socket, push the handle straight down to make the lever click into place, inserting the shorting wire across the interlock sensor at the bottom of the socket.
There is also a small wire from the battery harness that plugs into the receiving portion of the interlock. If you removed it during disassembly, but forgot to install it during the rebuild, the car will never know the interlock switch is installed.

The interlock switch installation instructions and a photo of the interlock connection wire are at this link

2008 Prius with red triangle will not go into drive or reverse | PriusChat

 

As mentioned above, P3004 has 3 related INFs that may help in diagnosing the problem, does your friends obd2 device offer the INFs (subcodes or detailed codes) for DTC P3004?

Below are some older workups from a 2004 manual, which may be useful.

Here is the workup for DTC P3004 with INF 131 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/3004131.pdf

Here is the workup for DTC P3004 with INF 132 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/3004132.pdf

Here is the workup for DTC P3004 with INF 133 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21bpm/3004133.pdf