BQ20Z45 CUV alarm not clearing

I have a 2-cell application.  

CUV Threshold is set for the default 2200mV.  Cell 2 is at 3500mV.  I reduce the voltage on cell 1 until it drops below 2200mV - CUV flag is set, TDA is set, discharge FET goes off.  Great.

CUV Recovery is set for the default 3000mV.  Cell 2 is at 3500mV.  Now I raise the voltage on cell 1 back to 3100mV, above the recovery threshold.  But the alarm does not clear.  What is it waiting for?

Thanks

Ed K