Issue in function without errors

Recently I've tried to challenge myself by trying to make a quiz game, however, as expected I've stumbled upon a error already and I can't resolve it. Well, there's no errors, but it's not working as intended, any suggestions on what to modify ?

Also, I'm a very beginner to C++ (still learning), so this might seem very dumb to others since I can already assume the problem is trivial.

Here's the code:

#include <iostream>
#include <cstdlib>
#include <stdlib.h>
#include <unistd.h>

bool strQuiz = false;


void welcomeScreen(void)
{
    std::cout << "Welcome to Quizlet" << std::endl;
    std::cout << "We'll ask you a bunch of questions" << std::endl; 
    std::cout << "When you're ready please type \"ready\" or \"exit\" to leave" << std::endl;
};

int startQuiz()
{
    int wait = 10;
    std::string userInput;
    while (!strQuiz)
    {
        getline(std::cin, userInput);
        if(userInput.compare("exit") == 0 && userInput.compare("") == 0) strQuiz = false;
        if(userInput.compare("ready") == 0)
        {
            std::cout << "Quiz starting in a few seconds...";
            sleep(wait);
        }
    }
    std::cout << "You've ended the Quiz";
    system("PAUSE");
    return EXIT_SUCCESS;
}

int main()
{
    welcomeScreen();
    startQuiz();
}

The issue is that although there are no errors, when I write ready or exit in terminal and hit enter nothing happens, it's just stuck at input. Issue is in startQuiz() function since welcomeScreen() function runs perfectly.

The loop I attempted in this project was from a previous project that I've done; Project: 8-Ball Game

FYI, I've attempted to change the function type since it was previously void but changed to int so that it can return termination status.

Edit:

Tried changing up the code, no change :(

int startQuiz()
{
    int wait = 100;
    std::string userInput;
    while (!strQuiz)
    {
        getline(std::cin, userInput);
        if(userInput.compare("exit") == 0) strQuiz = false;
        // Change
        else if(userInput.compare("") == 0)
        {
            userInput = "";
            std::cout << "Invalid Input, please try again" << std::endl;
        }
        if(userInput.compare("ready") == 0 && userInput.compare("exit") != 0)
        {
            std::cout << "Quiz starting in a few seconds...";
            sleep(wait);
        }
        // Change
    }
    std::cout << "You've ended the Quiz";
    return EXIT_SUCCESS;
}

Edit#2:

I apologize for wasting your time, I've realized the issue, I should've brainstormed more but I was honestly stuck. But your comments were very helpful, thank you.