I think I see the problem already. I think the reason you don't have anything light up on the PLC side is because the Transceiver get it's power on pin 8 - GRD and pin 9 - (7.5-15 VDC) That's on the second page of the manual I received from you.
On the PPI RS485/RS232 cable, pin 8 - is Clear to Send, and pin 9 - is Ring Indicator. Page 453 on the S7-200 manual.
That transciever board is depending on a standard 9 pin configuration. Although RS 232 is the protocol standard, the board's not getting any power.
From the symptoms you described, I'll bet this is it.