user58192: My MKR GSM 1400 works fine when connected to a computer (powered USB) and after opening a serial connection to it.  It does not when I plug it into a power supply. My power supply is a 5V 3A with a USB adapter.
void setup() {
  // put your setup code here, to run once:
  //...
  while (!Serial);
  //...
}

void loop() {
  // put your main code here, to run repeatedly:
  //...
}


user37622: If your sketch on an Arduino with native USB doesn't run if not connected to USB, always first check if you didn't forget to disable a dependence on Serial.  A common error is a while (!Serial) {} endless loop in setup().

58192: <p>My MKR GSM 1400 works fine when connected to a computer (powered USB) and after opening a serial connection to it.  It does not when I plug it into a power supply. My power supply is a 5V 3A with a USB adapter.</p>
<pre><code>void setup() {
  // put your setup code here, to run once:
  //...
  while (!Serial);
  //...
}

void loop() {
  // put your main code here, to run repeatedly:
  //...
}
</code></pre>
 37622: <p>If your sketch on an Arduino with native USB doesn't run if not connected to USB, always first check if you didn't forget to disable a dependence on <code>Serial</code>.  A common error is a <code>while (!Serial) {}</code> endless loop in setup().</p>
