I replaced an S703 + single channel STO (HWR 2.00) with a new device + dual channel STO (HWR 2.10). Now the device does not work. What went wrong?

The difference between these devices is the STO concept (single channel - dual channel). The new second STO input is on X4A pin 3. This pin has been used as XGND connection with the old drive. So the drive has no 24V supply voltage now. Please see the page Safety Concept S700.