Calling two Queue class function in a loop - c++

Question

I have problem with this code of mine. Whenever i call two function of the class, and in those class, there is if-else statement, and print the output on screen, it will only run the if clause of the two functions and not the else. How can i fix this?
For example:
This is my Queue.h file:
#ifndef QUEUE_H
#define QUEUE_H
class Queue {
private:
//private variables
int arr_size;
char *arr;
int head;
int tail;
int count;
public:
Queue(int); //constructor
//functions
int enqueue(char);
int dequeue(char&);
};
#endif
This is my Queue.cpp file:
#include <iostream>
#include "Queue.h"
using namespace std;
Queue::Queue(int size) {
//initializing
arr_size = size;
arr = new char[size];
for (int i = 0; i < arr_size; i++) {
arr[i] = NULL;
}
head = 0;
tail = 0;
count = 0;
}
int Queue::enqueue(char value) {
if (count<arr_size) //if array is not full, execute below
{
arr[tail++] = value; //pass value of first-to-last element in array
count++; //counting the input value
cout << "\nEnqueue Value: "<< arr[tail-1];
return 0;
}
else {
tail = 0;
cout << "\nArray is full. Value cannot be write: " << value;
return -1;
}
}
int Queue::dequeue(char &read_val) {
if (count !=0) { //if array has elements, execute below
read_val = arr[head]; //pass-by-reference the value of first-to-last element in array to parameter of function
cout <<"\nDequeue Value: "<<read_val;
arr[head] = NULL;
count--;
if (head++ == arr_size) {
head = 0;
}
return 0;
}
else if (count ==0) {
cout << "\nArray is empty. Cannot be dequeue";
return -1;
}
}
And this is what my Source file:
#include "Queue.h"
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Please enter the desired size of the array: ";
cin >> n;
char read_val = NULL;
Queue myqueue(n);
char arr[] = "Hello World, this is ELEC3150";
int size = sizeof(arr)-1;
int count = 0;
for (int i = 0; i < 5; i++) {
myqueue.enqueue(arr[count]);
count++;
myqueue.dequeue(read_val);
}
If i enter the size of the array to be less than 5, it must print the error message saying the array is full in the enqueue function and the array is empty in the dequeue function but did not.