C++ - fstream file don't create .txt file after a time

Question

I have a problem with file handling. More precisely I've written a code for exercising but after a time it won't make the .txt file. I don't know if the error is my computer or my code but I hope someone knows the answer. It's not the final stage but the problem started here. (This is a simple console application)

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

int Counter()
{
    static int taskID;
    cout << taskID++ << " - ";
}

int main(int argc, char const *argv[])
{
    char inputTask[256];
    string outputTask;
    string listAllTask = "-l";
    string addNewTask = "-a";
    string removeTask = "-r";
    string completeTask = "-c";

    if (argc == 1) {
        cout << "CLI Todo application" << endl;
        cout << "====================\n" << endl;
        cout << "Command line arguments:" << endl;
        cout << "-l   Lists all the tasks" << endl;
        cout << "-a   Adds a new task" << endl;
        cout << "-r   Removes a task" << endl;
        cout << "-c   Completes an task" << endl;
    } else if (argc == 2) {

        //create an object to access the file that containing the tasks
        fstream todoApp("tasks.txt", ios::ate | ios::in | ios::out);

        if (todoApp.is_open()) {

            if (string(argv[1]) == listAllTask){
                while (!todoApp.eof()) {
                    todoApp.seekg(0, ios::end);
                    if (todoApp.tellg() == 0) {
                        cout << "No todos for today! :)" << endl;
                    } else {
                        getline(todoApp, outputTask);
                        cout << Counter << outputTask << endl;
                    }
                }
            } else if (string(argv[1]) == addNewTask) {
                cout << "Enter the new todo:" << endl;
                todoApp.seekg(0, ios::end);
                cin.getline(inputTask, 120);
                todoApp << inputTask << endl;
                todoApp.close();
                cout << "-- your task has been saved --" << endl;
            } 
        } else {
            cerr << "Something went wrong, please, try again." << endl;
        }

        //todoApp.close();
    } else {
        cout << "Too many arguments!!!" << endl;
    }

    return 0;
}