PC > USB to RS485 Converter > RS485 Converter > Arduino. How to make it work?

I have this USB to RS485 converter connected to a computer. I also have this RS485 converter which is connected to an Arduino Uno (Arduino 5V to converter 5V0, Arduino GND to converter GND, Arduino RX (pin 0) to converter RXD, Arduino TX (pin 1) to converter TXD). The terminal blocks of both converters are connected together (Arduino converter GND to USB converter GND, Arduino converter A+ to USB converter A, Arduino converter B- to USB converter B).

I have a sketch on the Arduino which has Serial.begin(9600) on the first line of the setup() function. The sketch waits for commands and responds when it receives one. I have a simple C# program that opens the correct serial port, waits for 2 seconds, sends a command, waits for 1 second, then outputs the number of bytes waiting to be read. When I run this, it outputs 0 bytes. The power button on the Arduino converter is always illuminated, but neither the RXD or TXD LEDs illuminate at any point.

What can I do to make this work? If I connect the Arduino directly to the PC via the standard USB connection, unplug the USB converter, and run the C# program (changing the serial port name of course) then everything works fine, I receive 8 bytes, and the RXD and TXD LEDs on the still-connected Arduino converter briefly illuminate. I’ve tried connecting the two converters so it’s A+ to B and B- > A but that didn’t change anything.

Fixed. Arduino RX and TX pins were connected to the Arduino-side converter the wrong way around (should go to their opposites).