@MatiasV to switch on/off power to sensors and oled displays it is best to use a logic level P-channel Fet, something like an Si2305, it is not good practice to switch power to sensors/displays by switching the ground, it's OK for a relay though.

See this link
https://www.avrfreaks.net/forum/hi-side-fet-switch-low-voltage

Fixed -

You have to use void before() and place it before void presentation()

void before() {
pinMode (4, OUTPUT);
digitalWrite(4, HIGH);
}

void presentation()
{
// Send the Sketch Version Information to the Gateway
Serial.print("Send Sketch Info: ");
sendSketchInfo(SKETCH_NAME, SKETCH_VERSION);
Serial.print(SKETCH_NAME);
Serial.println(SKETCH_VERSION);
wait(LONG_WAIT);