BQ30Z554-R1: BQ30Z55 Can't turn on the CHG FET issue.

Part Number:BQ30Z554-R1

Hi sir,

     my customer is using BQ30Z55 for 2S battery pack ,now when they test the function, they find that if not connect the SMBUS, in charging mode , BQ30Z55 can't turn on the CHG Fet. it only can be active by connect the SMBUS or connect a load to discharge, the CHG FET can be turn on ,could you please help to suggest which setting will result this issue?