This is a question about the operation of ltc4120-4.2.

Hello. I am developing LTC4120-4.2 for research.
  When we fabricated the LTC 4120-4.2 PCB, we found that the charge voltage was 4.2V (Vin: 12V).
  However, it does not work when assembled together with the PCB board I am developing.
  It was working at first, but it's not working at any moment.

  Currently Vbat outputs 1.8V. Do you have any advice on this? The circuit I used is shown below.