Wake up on serial

I have some serial device( bluetooth) connected to the RX pin of the device .
I am trying to wake it up on connection .

So I can put the device to sleep, and I know that it gets the Rx signal, but it won’t wake up .

I must say , it worked once, then stopped working, so i know the setup is good (=led/rx)

There is the code to sleep and wake :

#include <avr/sleep.h>



const byte interruptPin = 2;



void sleepSystem()
{

      
      //attach interrupt 
       pinMode(interruptPin, INPUT_PULLUP); //INPUT DID NOT WORK
       EIFR = _BV(INTF1);
       attachInterrupt(interruptPin, wakeOnSerial, CHANGE); //RISING DID NOT WORK

  
     set_sleep_mode (SLEEP_MODE_PWR_DOWN);  
     sleep_enable();
     sleep_cpu ();
  
}



void wakeOnSerial()
{
  detachInterrupt(interruptPin);
  digitalWrite(LED1,HIGH);     // LED IS CERTAINLY FUNCTIONAL 
}

Any suggestion what wrong here ?

Thank you .

EDIT :

Have changed this line , now it works but the interrupt happens right when I attach it :

attachInterrupt(digitalPinToInterrupt(interruptPin), wakeOnSerial, FALLING); //RISING IS THE SAME