Possible problem and solution:

Be sure that your unit is powered and the communication cable is connected securely on both ends.

The Lexium ILP/ILT default baud rate is 9600 baud.
Be sure that the Lexium CT baud rate is set to 9600 baud.

Check to be sure that in the lower right hand corner of the terminal window it shows Connected.
If it shows disconnected, then double-click the word Disconnected or click on the appropriate phone icon.