It is required that you start the ethernet connection with Ethernet.begin(mac). You mention it with a comment, but never start it. I added it below.
void setup()
{
// start the serial library:
Serial.begin(9600);
// set display brightness
Serial.write(0x7C);
Serial.write(157);
// set screen size in case LCD gets derpy...
Serial.write(0xFE);
Serial.write(6);
Serial.write(0xFE);
Serial.write(4);
delay(4000);
// start the Ethernet connection:
if(!Ethernet.begin(mac)) Serial.println("ethernet failed");
else Serial.println(Ethernet.localIP());
// set up soft reset button
////attachInterrupt(0, softReset, CHANGE);
// clear screen
clearDisplay();
}