I looked at the PDF. Wow.
I'm not sure what the end resistor is doing.
I have had a very similar problem and this is not going to be nice what I am about to say, so please get ready.
If you can: get another USB-RS485 converter, so you have two of them.
Connect them to USB ports and open a program like a terminal which you use to talk to remote devices.
You will have two of these running. One on one device and one on the other.
Set them both to the same speed/stop and parity.
Or use two different machines if you can.
Connect #1's TX to #2's RX and #1's RX to #2's TX at the RS485 side of things. Basically a "null modem".
Type on one and see if you get that on the other program.
Though this is not 100% going to fix the problem, it will take you a long way to knowing what is going on.
Until you can prove that is working, you are really wasting time.
I got stuck with a USB-RS232 converter and wasted about 7 months because of a silly thing.
Oh, just to also check:
You did reverse the TX/RX lines? (You didn't put TX to TX and RX to RX)