The WFCO "reverse polarity" fuses are likely blown. Replace all even if just one is blown.
The new 6s at 12.28 are low from being on the shelf so long. "they need a good charging up to "full" and then do an "overcharge" on them to desulfate/destratify them from sitting so long undercharged. After that, take an hydrometer reading in all cells and note the number. That is your "baseline SG" you want to see in the future when you are going for a 100% SOC.
BTW, PD is not the only other converter in the world besides WFCOs. There is also PowerMax. Each brand has its own fan club. :)