PTT keying

[Donsass]

I have the 706MK2G software installed and mainly working under windows 7. Unfortunately the PTT key function does not seem to work. My configuration is:  COM1, 9600,8,1,N,RTS and DTS = OFF   PTT is enabled on COM1 :RTS  PTT key is CTRL.  The Tune function works but neither pressing the CTRL nor clicking on the mic icon (although the red light glows on) seems to work. I have changed  PTT and COM1 configurations using DTR, serial port modes and different com speeds but nothing works.
Do you have any suggestions.
Thank you