Atmega328P FTDI 5V USB Serial Communication
You probably need to get an oscilloscope involved so that you can see signal levels and whether any actual serial signals are appearing. 

Do know that the number one mistake made in connecting up serial ports like this is getting the Tx and Rx signals cross wired. The FTDI cable will be labeled with Tx being its output signal pin on pin 4 (orange wire) and its Rx being its input signal on pin 5 (yellow wire). 



You must connect the Tx pin of the FTDI cable to the Rx pin on the AVR. Likewise you must connect the Tx pin of the FTDI cable to the Tx pin on the AVR.

The big mistake that is often made is that folks connect the two Tx signals together and the two Rx signals together.