Sigfox Down after deep sleep

Using Arduino Networking, Protocols, and Devices
1

Hello everyone,

I have some troubles with deep sleep and Sigfox with a arduino nano.

I want to use it with a 9V battery so I have to turn the arduino in deep sleep while i dont need to send data.

So I use :

My code :

 // SLEEP MODE
        Serial.print("SLEEP MODE");
        delay(100); //delay to allow serial to fully print before sleep
        sleep.pwrDownMode(); //set sleep mode
        //Sleep till interrupt pin equals a particular state.
        sleep.sleepPinInterrupt(intPin,RISING); //(interrupt Pin Number, interrupt State)
        // Wake UP
        Serial.print("WAKE UP");
        delay(100); //delay to allow serial to fully print after wake up

I don't understand why my sigfox modem is down after this.

A reset is not enough to re-use it, I have to unplug an re plug the USB to use the Sigfox modem again.

Have you any ideas ?
I think there is a link with UART but...

Thanks a lot.

Franck