BQ77910A：I cannot charge

I use BQ77910 as below。

the BAT Voltage=22.07V（6S Polymer Lithium-Ion Battery）,After I insert a charge(CC=1.8A)，there is no charge current。

I messure  those pins：reference VSS

Pin CHG=11.8V

Pin DSG=0.9V

Can anybody help me?