AD8605 4 level filter can't work

Hello, I design a 4 level filter in accordance with the online design wizard of ADI, as follows, but, it finds that the second level is output 0V. Why?  how to adjust and test?

U1:AD8605;

Single power supply 4V;

VREF = 2V;

The first stage output 5mV sine wave, offset +10mV;

The second level output is 0.