Solution:

When using an I/O unit with Repeater mode enabled: In Peer-to-Peer mode, the repeater must be set for Modbus mode, and the repeater I/O channels are NOT accessible. This is done to keep the repeater device from accidentally responding to Peer-to-Peer packets sent by the Master device. In Modbus Mode, the Radio Modem will be set as a Repeater End Node, and the I/O Repeater check box is enabled. The I/O will be set for Modbus with a unique Modbus Address. The repeater I/O channels ARE accessible when polling its Modbus address.