The OUT pins of the DS4424 will not be in high impedance until a proper voltage is applied to Vcc.
Vcc of the DS4424 must be powered before or at the same time as the power of the source it is controlling.
If there is voltage applied to the OUT pins before Vcc is applied, then -
1. The internal ESD diode between OUT and Vcc pins may turn ON , causing the voltage of the power supply being controlled to reach a very large value
2. The Absolute Maximum Rating of the OUT pins i.e. (Vcc + 0.5V) may be exceeded causing damage to the DS4424