I'me unable to see a login prompt from the 9-Pin serial port on the front panel of the MR4800E controller.

That db-9 connector on the front of the MR4800E is not used (it was intended for future use but never implemented). The "config port" the owner's manual is referring to, is on the back of the CC4800 chassis (directly behind the MR4800E controller). It's a DB-25 connector. The DB-25 connector config port is a DCE interface (just like the db-25 for each modem). So, you would use a standard DB-9 to DB-25 cable (when connecting from a DTE DB-9 of a laptop\PC to the MR4800E controller). The serial communication parameters of the terminal must be set to 115200 bps, 8 Data Bits, 1 Stop Bit, No Parity and Flow Control must be off (set to none).