In the manual for the IC-746, the remote port is identified incorrectly. The image from the manual identifies the Remote port as the Speaker Port and the Speaker port as the Remote port.

If the USB-RTS01 cable is connected to this port, communications will not be possible from the radio to the programmer or to any other remote control software. This just is not the right port.

Shown here is the cable connected correctly to the back of the radio.