P3000 after a long struggle

This is a bit of a TLDR, but I am stuck.
2008 w/180k. I replaced a few modules about 18 months ago, and had no issues until about 5 weeks ago. I chose to try to recondition the cells (and utilize my best cells and the best of the lot I bought last time). After almost 4 weeks of cycling cells with great results I replaced the worst and reinstalled the HV battery. Alas, the 12v was seriously discharged, and a quick jump got it started. All codes gone. Drove and ran for 20ish minutes. When I turned it off, everything was dead again. Repeated a jump with no issues, then put the battery on a charger and tested it after a second run (5.7v, yikes). Anyway, trickle charged for 2 days and reinstalled. Started right up, but then immediately threw the P3000 (makes me think it’s not a cooling issue.)
I do not have Techstream, but free DrPrius, and CarScanner apps.
Here’s what I’ve checked:
Other than the code, drives as normal (though fuel gauge is also blinking empty despite being very full)
HV Battery 220 v
All cells have greater than 4.0 Ah capacity, majority well over 5.0.
All cells within 0.12v after cycling up to 80% and down to 20%(balanced for a week waiting for the bus bars)
12v: 12.4v engine off
All new bus bars and nuts
All connections and related fuses (high desert car with zero rust)
Hybrid pack cooling blower works (tested at 12v, and from 0.8-2.0 amps)
oh, and I noticed when raising the temperature of the battery fan threshold, the red triangle stays off, until the temps rise and the car tries to turn the blower on. Then the code is thrown again within 5 seconds.
This is my third/ fourth time battery out, so it’s easy now, BUT,
What am I missing?