Argon Serial1 Not Transmitting

Troubleshooting
3

Thanks for the fast reply! Great followup test; sadly it didn’t work out. Here’s my code:

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  delay(100);
  Serial1.begin(9600);
  delay(100);
  Serial.println("Ready!"); //Write to USB
}

void loop() {
  if (millis() % 1000 == 0) {
      Serial1.println("Hello");   //Write to Serial1
      Serial.println("Wrote to Serial1"); //Write to USB
  }
  if (Serial1.available()) {
      byte i = Serial1.read();  //Read from Serial1
      Serial.print(i);        //Write to USB
  }
}

And my USB Serial output:

Serial monitor opened successfully:
Ready!
Wrote to Serial1
Wrote to Serial1
Wrote to Serial1
Wrote to Serial1
...

Pinky swear I have TX (D9) and RX (D10) connected together.