jQuery Button is Not Showing The Next Question

I’m making a quiz about YouTube. I have three working questions, but the fourth one isn’t working with the others the way it’s supposed to. The next buttons work, but for the switch between the third and fourth questions does not switch all the way. When you click it, it will hide the third, but it won’t show the fourth. I’ve looked over the code multiple times, but I can’t fine the problem.

CSS:

.question1 {
  text-align: center;
  height: 20px;
  width: 440px;
  background-color: lightblue;
}

li {
  position: relative;
  left: -20px;
  cursor: pointer;
  padding-top: 15px;
  padding-bottom: 15px;
}

.check {
  font-size: 20px;
  color: green;
}

span {
  font-size: 15px;
}

.score {
  position: absolute;
  top: 0px;
  left: 98.5%;
  font-size: 25px;
}

.q1a3cover {
  color: green;
}

.next1 {
  position: absolute;
  top: 125px;
  left: 500px;
  height: 50px;
  width: 75px;
  background-color: cadetblue;
  border: 3px solid olivedrab;
  border-radius: 5px;
  cursor: pointer;
}

.question2 {
  text-align: center;
  height: 20px;
  width: 475px;
  background-color: lightblue;
}

.q2a3cover {
  color: green;
}

.next2 {
  position: absolute;
  top: 125px;
  left: 500px;
  height: 50px;
  width: 75px;
  background-color: cadetblue;
  border: 3px solid olivedrab;
  border-radius: 5px;
  cursor: pointer;
}

.question3 {
  text-align: center;
  height: 20px;
  width: 310px;
  background-color: lightblue;
}

.q3a2cover {
  color: green;
}

.next3 {
  position: absolute;
  top: 125px;
  left: 500px;
  height: 50px;
  width: 75px;
  background-color: cadetblue;
  border: 3px solid olivedrab;
  border-radius: 5px;
  cursor: pointer;
}

.question4 {
  text-align: center;
  height: 20px;
  width: 310px;
  background-color: lightblue;
}

.q4a4cover {
  color: green;
}

.next4 {
  position: absolute;
  top: 125px;
  left: 500px;
  height: 50px;
  width: 75px;
  background-color: cadetblue;
  border: 3px solid olivedrab;
  border-radius: 5px;
  cursor: pointer;
}

html:

<script src="https://code.jquery.com/jquery-1.12.3.js"></script>

<div class="scorebox">
  <div class="score"><b>0</b></div>
</div>

<!-- question one ↓ -->
<div class="q1">
  <div class="question1"><b>How many subscribers do you need to make a community post?</b></div>

  <ul class="q1as">
    <li class="q1a1">0 <span class="q1x1">❌</span></li>
    <li class="q1a2">500 <span class="q1x2">❌</span></li>
    <li class="q1a3">1000</li>
    <li class="q1a3cover">1000 <span class="check">✔</span></li>
    <li class="q1a4">1500 <span class="q1x3">❌</span></li>
    <li class="q1a5">2000 <span class="q1x4">❌</span></li>
  </ul>

  <button class="next1"><b>Next</b></button>
</div>

<!-- question two ↓ -->
<div class="q2">
  <div class="question2"><b>What is the maximum amount a replies you can have on a <i>comment</i>?</b></div>

  <ul class="q2as">
    <li class="q2a1">0 <span class="q2x1">❌</span></li>
    <li class="q2a2">250 <span class="q2x2">❌</span></li>
    <li class="q2a3">500</li>
    <li class="q2a3cover">500 <span class="check2">✔</span></li>
    <li class="q2a4">750 <span class="q2x3">❌</span></li>
    <li class="q2a5">1000 <span class="q2x4">❌</span></li>
  </ul>

  <button class="next2"><b>Next</b></button>
</div>

<!-- question three ↓ -->
<div class="q3">
  <div class="question3"><b>What is the most viewed video on YouTube?</b></div>

  <ul class="q3as">
    <li class="q3a1">"Despacito"- Luis Fonsi<span class="q3x1"><b> -7.64B</b> ❌</span></li>
    <li class="q3a2">"Baby Shark Dance"- Pinkfong</li>
    <li class="q3a2cover">"Baby Shark Dance"- Pinkfong<span class="check3"><b> -9.75B</b> ✔</span></li>
    <li class="q3a3">"Shape of You"- Ed Sheeran<span class="q3x2"> -5.54B ❌</span></li>
    <li class="q3a4">"Uptown Funk"- Mark Ronson<span class="q3x3"> -4.38B ❌</span></li>
    <li class="q3a5">"See You Again"- Wiz Khalifa<span class="q3x4"> -5.34B ❌</span></li>
  </ul>

  <button class="next4"><b>Next</b></button>
</div>

<!-- question four ↓ -->
<div class="q4">
  <div class="question4"><b>What does YouTube send you when you reach 50,000,000 subscribers?</b></div>

  <ul class="q4as">
    <li class="q4a1">Silver Play Button<span class="q4x1"><b> - 100,000</b> ❌</span></li>
    <li class="q4a2">Diamond Play Button<span class="q4x2"><b> - 10,000,000</b> ❌</span></li>
    <li class="q4a3">Gold Play Button<span class="q4x3"><b> - 1,000,000</b> ❌</span></li>
    <li class="q4a4">Ruby Play Button</li>
    <li class="q4a4cover">Ruby Play Button<span class="check4"><b> - 50,000,000</b> ✔</span></li>
    <li class="q4a5">Nothing<span class="q4x4"> ❌</span></li>
  </ul>

  <button class="next4"><b>Next</b></button>
</div>

jQuery:

score = 0;

$(document).ready(function () {
  $("span, .check, .check2, .check3, .check4").hide();
  $(".q1a3cover").hide();
  $(".q2a3cover").hide();
  $(".q3a2cover").hide();
  $(".q4a4cover").hide();
  $(".q2").hide();
  $(".q3").hide();
  $(".q4").hide();

  //question 1 ↓
  $(".q1as").click(function () {
    $(".check").show();
    $(".q1a3cover").show();
    $(".q1a3").hide();
  });

  //answers ↓
  $(".q1a1").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q1x1").show();
  });
  $(".q1a2").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q1x2").show();
  });
  $(".q1a3").click(function () {
    $(".score").text((score += 1));
  });
  $(".q1a4").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q1x3").show();
  });
  $(".q1a5").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q1x4").show();
  });

  //next button ↓
  $(".next1").click(function () {
    $(".q1").hide();
    $(".q2").show();
  });

  //second question ↓
  $(".q2as").click(function () {
    $(".q2a3cover").show();
    $(".q2a3").hide();
    $(".check2").show();
  });

  //answers ↓
  $(".q2a1").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q2x1").show();
  });
  $(".q2a2").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q2x2").show();
  });
  $(".q2a3").click(function () {
    $(".score").text((score += 1));
  });
  $(".q2a4").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q2x3").show();
  });
  $(".q2a5").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q2x4").show();
  });

  //next button ↓
  $(".next2").click(function () {
    $(".q1").hide();
    $(".q2").hide();
    $(".q3").show();
  });

  //third question ↓
  $(".q3as").click(function () {
    $(".q3a2cover").show();
    $(".q3a2").hide();
    $(".check3").show();
  });

  //answers ↓
  $(".q3a1").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q3x1").show();
  });
  $(".q3a2").click(function () {
    $(".score").text((score += 1));
  });
  $(".q3a3").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q3x2").show();
  });
  $(".q3a4").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q3x3").show();
  });
  $(".q3a5").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q3x4").show();
  });

  //next button ↓
  $(".next3").click(function () {
    $(".q1").hide();
    $(".q2").hide();
    $(".q3").hide();
    $(".q4").show();
  });

  //fourth question ↓
  $(".q4as").click(function () {
    $(".q4a4cover").show();
    $(".q4a4").hide();
    $(".check4").show();
  });

  //answers ↓
  $(".q4a1").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q4x1").show();
  });
  $(".q4a2").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q4x2").show();
  });
  $(".q4a3").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q4x3").show();
  });
  $(".q4a4").click(function () {
    $(".score").text((score += 1));
  });
  $(".q4a5").click(function () {
    $(this).css("color", "#9A1B1E");
    $(".q4x4").show();
  });

  //next button ↓
  $(".next4").click(function () {
    $(".q1").hide();
    $(".q2").hide();
    $(".q3").hide();
    $(".q4").hide();
    $(".q5").show();
  });
});

>Solution :

change :

<button class="next4"><b>Next</b></button>

in question three Section to:

<button class="next3"><b>Next</b></button>