Attiny85 and Interrupt

Hi, Presently using Arduino as an in-system programmer for a Attiny85. Everything works fine with simple program , but it doesn't work when it includes interrpt pin.

-Sensor connected to the Attiny pin 6(int0) . Should I enable something else? Maybe the wrong pin? Thank you for any hint

Part of the code with interupt call :

void setup() {                                      // Begin setup
  pinMode(AC_pin, OUTPUT);                          // Set the Triac pin as output
  pinMode(LED, OUTPUT);                             // Set the LED pin as output
  attachInterrupt(0, zero_cross_detect, RISING);   // Attach an Interupt to Pin 6 (interupt 0) for Zero Cross Detection
  Timer1.initialize(freqStep);                      // Initialize TimerOne library for the freq we need
  Timer1.attachInterrupt(dim_check, freqStep);      
  // Use the TimerOne Library to attach an interrupt
  // to the function we use to check to see if it is 
  // the right time to fire the triac.  This function 
  // will now run every freqStep in microseconds.                                            

By “pin 6” in the comment, do you mean physical pin 6 on the PDIP, SOIC or TSSOP package? The datasheet shows INT0 as being on pin 7.