Using pointers to duplicate and grow an existing array

I am failing to reach expected output when testing my 'grow'and 'subArray' functions. I've tried dereferencing back and forth in the function and also in main(). I'm wondering if there's something wrong with my memory allocation that is causing the lapse. I am extremely stuck and was hoping someone could potentially see something that I am missing, thanks.

#include <iostream>
#include <iomanip>
using namespace std;

bool isSorted(int *arr, int size){
    for(int index = 0; index < size - 1; index ++){
        if(*(arr + index) > *(arr + index + 1)){
            return false;
        }

    }
    return true;
}


double chain (int totalInches, int *feet, int *inches){
    *feet = totalInches/12;
    *inches = totalInches%12;
    return *(feet)*3.49 + *(inches)*.30;
}

int *grow (int *arr, int size){
    int *newArray;
    newArray = new int[size*2]; //alocate new array
    for(int i = 0; i < size*2; i+=2){
        *(newArray + i) = *(arr+i);
        *(newArray + i + 1) = *(arr+i);    
    }
    return newArray;

}

int *duplicateArray (int *array, int size) {

    int *newArray;
    if (size <= 0)
    return NULL;
    newArray = new int [size]; //allocate new array
    for (int index = 0; index < size; index++){
        newArray[index] = array[index]; //copy to new array
    }
    return newArray;
}

int *subArray( int *array, int start, int length){
    int *result = duplicateArray(array,5);
    return result;
}

void showArray( int *arr, int size){
    for(int  i = 0; i < size; i ++)
    {
        cout << *(arr + i) << " ";
    }
}
int main(){

    int size = 8;
    int testArray[] = {1,2,3,4,5,6,7,8};
    cout << "testing isSorted: " << endl;
    cout << "test data array 1: ";
    showArray(testArray, size);
    cout << endl;
    cout << "Expected result: true" << endl;
    cout << "Actual result: " << boolalpha << isSorted(testArray, size);
    cout << endl;
    int testArray2[]= {8,7,6,5,4,3,2,1};
    cout << "test data array 2: ";
    showArray(testArray2, size);
    cout << endl;
    cout << "Expected result: false" << endl;
    cout << "Actual result: " << boolalpha << isSorted(testArray2, size);
    cout << endl << endl << endl;
    int chainTest = 53;
    cout << "Checking chain for 53 inches: " << endl;
    cout << "Expected result: 15.46 " << "  " << "feet: 4 " <<
    "  " << "inches: 5"<< endl;
    int in;
    int ft;
    cout << "Actual results : " << chain(chainTest,&ft,&in);
    cout << "   " << "feet: " << ft << "   " << "inches: " << in << endl;
    cout << endl << endl;
    cout << "testing grow: " << endl;
    cout << "test data 1: ";
    showArray(testArray, size);
    cout << endl;
    cout << "Expected result: 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 " << endl;
    cout << "Actual results: " << *(grow(testArray, size));
    cout << endl << endl;
    cout << "testing subArray:" << endl;
    cout << "test data: ";
    showArray(testArray, size);
    cout << endl;
    int start = 5;
    int length = 3;
    cout << "start: " << start << " " << "length: " << length << endl;
    cout << "Expected result: " << "6 7 8" << endl;
    cout << "Actual result:   " << *(subArray(testArray, start, length));
    cout << endl;

    return 0;
}

Output:

As you notice, the loop is terminating after one traversal. The grow function is intended to duplicate and expand. In other words, it's supposed to make a copy of itself and append as it traverses. Any ideas as to why I am getting hung on the first element of the array?