Interrupt on port B not working

[AD76XYZ]

Hi,
I was testing port b interrupt.
Am using.
PIC16F886 @4MHz Internal Osc.
CCS C Version 4.105

I have connected LED on A0 and giving low signal on RB7-RB4 but no LED glow.
The pins RB7-RB4 is high, checked by logic probe.
Please where I did mistake.
Whenever I give logic zero to any of pin RB7-RB4 the LED should glow.

#include "KBD_WakeUp.h" 


#use delay(4000000) 
#int_RB 

#define LED PIN_A0 



void  RB_isr(void) 
{ 
clear_interrupt(INT_RB); 
output_bit(LED, 1); 
delay_ms(500); 
} 




void main() 
{ 

   setup_adc_ports(NO_ANALOGS|VSS_VDD); 
   setup_adc(ADC_CLOCK_DIV_2); 
   setup_spi(SPI_SS_DISABLED); 
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); 
   setup_timer_1(T1_DISABLED); 
   setup_timer_2(T2_DISABLED,0,1); 
   setup_ccp1(CCP_OFF); 
   setup_comparator(NC_NC_NC_NC);// This device COMP currently not supported by the PICWizard 
   enable_interrupts(INT_RB); 
   enable_interrupts(GLOBAL); 
   setup_oscillator(OSC_4MHZ); 

   // TODO: USER CODE!! 
    
  
    
    
    
   set_tris_b(0x0F); 
   ext_int_edge(H_TO_L); 
   output_bit(LED,0); 
    
   while(1) 
   { 
   } 

}