Basic Serial communication Arduino <> Max/MSP not working

Hi there,

I'm trying to get very basic serial communication going between Arduino (UNO R3) and Max/MSP (Max/MSP 8 running on MacOS Sonoma). But without any results. When I open the Serial monitor in Arduino (which I of course closed again when testing things through Max...) it works just fine, so I'm assuming the connection can't be the issue. Does anyone have an idea what I'm doing wrong here? Really hope someone will be able to assist...

Anne-Jan

int LED_pin = LED_BUILTIN;
int value1 = 300;

void setup() {
  Serial.begin(9600);
  pinMode(LED_pin, OUTPUT);
}

void loop() {
  if (Serial.available()) {
    value1 = Serial.read();
  }

  digitalWrite(LED_pin, HIGH);
  delay(value1);
  digitalWrite(LED_pin, LOW);
  delay(value1);

  Serial.println("hello");
}