This is what I think the situation is
EZIComm A connected to the ISY has no problem communicating with EZIComm B connected to the EZIO8SA
EZIComm A connected to computer serial port, using the SHN Utility, cannot communicate with EZIComm B connected to the EZIO8SA.
The screen capture shows the SHN Utility connected to an EZIComm (firmware v.9C) successfully as the detail tabs across the top are displayed. The SHN Utility uses the same Serial PLM commands as the ISY is using yet one works the other does not.
There could be issues with the lap top plugged into the same location as the ISY/PLM causing communications problems but the ISY would also have trouble communicating.
I have no explanation for these results. The EZIComm B will ultimately not work with the EZIO8SA but it has to do with the location of the link records, not the ability to do basic communication with EZIComm B. Sorry, but I am at a lose to suggest the next step.