MKR Fox 1200 doesn't wake up from sleep 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 &gt; 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.
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() {
}