Incomplete charge and wrong voltage

I have an AC200P EU version. This is powered by 16S LiFePo4 as far as I know. Now I have the problem that it doesn’t charge fully. The BMS tells me a voltage of 3.3V per cell at 100% state of charge. Only about 800Wh can be extracted. I tried several times to repeat discharging and charging from 0 to 100%. I think the problem is that charging stops when the battery voltage reaches 56V. But if the panel shows 56V at the same time, it shows a cell voltage of 16 x 3.3V. That can’t come together.