MKR Fox 1200 doesn't wake up from sleep

Question

I have a Sigfox Arduino meassuring some sensors, sending it to the cloud and then falling asleep.

void setup()
{
Serial.begin(9600); 
  while (!Serial) {};
  if (!SigFox.begin()) {
    Serial.println("Shield error or not present!");
    return;
  }
  SigFox.debug();
  delay(100);
  SigFox.end();
}


void loop() 
{
SigFox.begin();
  delay(100);
  SigFox.status();
  delay(1);
  SigFox.beginPacket();
  SigFox.print("123456789012");
  int ret = SigFox.endPacket(true);

  if (ret > 0) {
    Serial.println("No transmission");
  } else {
    Serial.println("Transmission ok");
  }
  Serial.println();
  SigFox.end();
LowPower.sleep(20000);
}

The Issue I have is that the sending to the backend doesn't work when leaving the sigfox.debug() away and that it doesn't wake up from the sleep. It stays in sleep forever.

Answer 1

Looks like same problem as described in https://forum.arduino.cc/index.php?topic=483636.0 Solution described in that thread: Add

LowPower.attachInterruptWakeup(RTC_ALARM_WAKEUP, alarmEvent0, CHANGE);

to setup() and create a dummy function

void alarmEvent0() {
}