Atmega 32u4 and VBUS/sleep mode

hello,
for project first used arduino leonardo , have built our own.
for tests working on the sparkfun promicro board.
our problem deal usb functionalities. want put atmega in eco power mode , wake external interruption or interrupt vector of usb.
but when set vbuste bit of usbcon register atmel isn't recognized more computer, , flag vbus doesn't rise ( full_bat_warn() doesn't launch).

here main part of program:

code: [select]

void setup()
{
  init_io();  // input , output setup
  init_pwm();//init battery charge
  init_accelerometer(int_pin_accel);
 
  strip.begin();
  strip.show(); // initialize pixels 'off'
  usbcon |= _bv(vbuste);
  delay(1000); //delay connect via usb before sleep_mode()
}
void loop()
{
  char motion;
  char shake;
  static char mode = off_mode;
 
  if(update_motion_flag){
    update_motion_flag = 0;
    shake = detect_motion(&motion);
  }
  switch (mode)
  {
    case off_mode :
       entersleep();
        if(shake)
        {
          if(vbus)
            full_bat_warn();
          mode = normal_mode;
        }
    break;
   
    case charge_mode :
        charge_control();
    break;
   
    case low_b_mode :
    break;
   
    case normal_mode :
      if (state_batterie()==empty)
      {
         low_bat_warn();
         mode = off_mode;
         break;
      }
      mode = launch_normal();
    break; 
  }
}

void entersleep(void)
{
  set_sleep_mode(sleep_mode_pwr_down);
 
  sleep_enable();
 
  sleep_mode();
 
  /* program continue here. */
 
  /* first thing disable sleep. */
  sleep_disable();
}

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