Can't Retrieve Upper & Lower Bands from iBand

I'm trying to get the upper and lower values from iBand...

void OnTick()
{
    double upperBand[];
    double lowerBand[];
    double range;

    int handle = iBands(_Symbol, _Period, 20, 2, 0, PRICE_CLOSE);
    // CopyBuffer(handle, which band, period, no. values, where to store)
    CopyBuffer(handle, 1, 0, 1, upperBand);
    CopyBuffer(handle, 2, 0, 1, lowerBand);
    
    
    // Use the upper_band and lower_band variables
    Print("Upper Band: ", upperBand[0]);
    Print("Lower Band: ", lowerBand[0]);
    range = upperBand[0] - lowerBand[0];
    Print("Range: ", range);
}

However the print functions reliably return an identical value, one that appears in fact to be the middle band value.

Of course, x = x, and so the range is always 0.

As I'm getting no error code and the data set is intact, I'm not even sure how to trouble shoot?

You are initializing the indicator incorrectly. Try the following

int   handle_iBands;

int OnInit()
{
   handle_iBands = iBands(_Symbol, PERIOD_CURRENT, 20, 2, 0.0, PRICE_CLOSE);
return(INIT_SUCCEEDED);
}

void OnTick()
{
   double Upper[], Lower[], range;
   CopyBuffer(handle_iBands, 1, 0, 10, Upper);
   CopyBuffer(handle_iBands, 2, 0, 10, Lower);

   Print("Upper Band: ", Upper[0]);
   Print("Lower Band: ", Lower[0]);
   range = Upper[0] - Lower[0];
   Print("Range: ", range);
}