Going down the settings in minicom, it should be:
A - /dev/(device for the com port you are using)
E - 115200 8N1
F - No
F - No

If these match your setup, try a different serial cable, or try some other device to verify the one you are using is working. It's a standard null model cable. Beyond that, it could be a problem with the serial port on either your system or the empeg.

Another test you could do is try to see if emptool can talk to the empeg via serial.