Well here goes, i have been at this for 2 weeks with over 200 google links clicked trying to get this to work.

I have 2 custom built cables that i took apart and manually verified vs polling software specs.
I have tried with Belkin USB to Serial Converter and PCI Serial Card.

Register Settings:
2690 1000 0000 0000
6110 000001
6111 00
6112 07
6113 002013
6115 007
6220 000
(i have tried many variations of the above settings as well)
Software settings match the registers set port speed (38400) i have also tried 2 different polling programs.
Hardware is all plugged in correct (it instantly fails if its not hooked up right) currently it just times out instead of insta' failing

I have tried both register com ports, i have tried program resets (with the service key) after com port changes. No sales are pending and the register is set to reg mode.
the pc sends packets but the register never responds.
Rom Version RCC2C (was told it was compatible with the softwares RCC2A eprom version selection)

No other devices are hooked up to the register.

I have lost half of my head of hair over this and I am really hoping to get this working before i completely bald myself.

I also came across the same issue & manage to get it fixed. Here I would like to share the settings that I been using:

2690 1000 0000 0000
6110 000001
6111 00
6112 06
6113 002013
6115 007
6220 010

And make sure you set your COM port to match your speed under your computer setting.