Your problem is RTS/CTS handshaking.
Your cable is set to require that handshake, you need to modify the cable to ignore the handshake, like the link I provided.
You will need to short pins 4 and 5 together on the PLC side.
Also short pins 7 and 8 on the PC side.
I use the cable diagram from the posted link to the DB9 port. I do not have the CQM1-CIF02 cable.
See attached pdf file.