please refer to the Figure 13. in the UM11421 attached. Please also refer to the following notes.
Please refer to the section 3.2 in an UM11421 attached. You need to connect a battery pack to JP1 connector with minimally 3, maximally 6 Cells. To use the Cells is mandatory. Easiest is to connect battery pack with 6 Cells.
And you need to set the jumpers along the number of Cell you have connected. Please refer to the page 3. in the schematic attached.
The individual Cell voltage must be within the voltage range stated in the Table (-0.3V to 5V) in the MC33772B product page.
The Supply voltage is stated from 6V to 30V, but for the RDDRONE-BMS772 the maximum supply voltage is lower. Only 26V. So please follow the UM11421 definition to be safe.
I have checked your connection and it is correct.
Please measure the Cell #4 voltage with the multimeter on the JP1 connector? The VBATT voltage shows 15.5V, which is approximately 4*3.9V. Perhaps the cable on the Cell #4 is damaged.
With Best Regards,