Input Shield V3 XBee not recognized

I cannot get the XBee module to be recognized on the Input Shield V3.

I have 3 XBee modules that are both configured properly and can be read by the Digi X-CTU software when plugged into your XBee pro shield stacked directly onto my Arduino Uno board

The XBee modules can also be read when plugged into your XBee pro shield that's stacked on top of the Input Shield V3 that is in turn plugged into the Arduino.

However, if I plug the Input Shield V3 alone into the Arduino, and install the XBee module on it, the XBee module is not recognized.

I am probably doing something wrong, but haven't been able to find any detailed information about the proper procedure for getting this to work. Any help would be appreciated.