Over the past few days I've checked all the TX and RX lines multiple times - or so I thought. The one I did not check was the physical DB9 connector on the RS232/TTL adapter which turned out to be the problem. The pinouts did not pair up properly with the Keyence unit. I made a little DB9 M-F cable that reversed pins 1-5 and voila!
Thanks for your Reply Mike - greatly appreciated!