Was all of the following done?

SETUP OF CRESTRON
HARDWARE:
Baud Rate - 9600
Parity - Odd
Data Bits - 8
Stop Bits - 1
VENDOR FIRMWARE: For Advent:
Control Panel Version 1.6
Automation Module Version 3.43
For Concord:
Version 2.5 or later
VENDOR SETUP: You must use the GE Printer/Automation module to
enable communications with the Crestron system. This
module will attach to the GE bus, and will provide an
RS232 port for use by the Crestron system. When
ordering this module you must specify that it is for a
Crestron control system. Use the 9 pin connector.
The DIP switches inside the module should be set as
follows:
1 - On
2 - Off

This setup is as easy as it gets, just about plug and play.  If you power down the security system, then power back up with Automation module plugged in, it learns in the automation module and starts talking to Crestron.  If your Crestron module is proven and has worked before, and the programming is as it should be, then you have one of two possible issues: bad cable (straight through is used), or the automation module itself is bad.  I have seen bad automation modules, so don't doubt that part too much. There are occasions in which a reboot of Security system AND a reboot of Crestron is what got things going.
Again, this is considering the Crestron module has been proven to work before and programming within Simpl is properly connected.

Just thought I'd post that this issue was finally resolved. Here's what happened:

Apparently, when the part is ordered through ADT Security, they bring you an automation module with model number 59-739-03-IS. This will NOT work with Crestron. This model is supposedly for "Interactive Services" automation...whatever that is. The correct model number is 60-783-02 which looks literally identical to the 59-739-03-IS.

The 59-739-03-IS does not come enclosed in a protective case however, but the 60-783-02 does.

So there you have it, I will be returning the 59-739-03-IS to ADT.

Thank you everyone for all your help.