Form check prevent from submiting even when everything is ok

const form = document.getElementById('form');
const username = document.getElementById('username');
const email = document.getElementById('email');
const password = document.getElementById('password');
const password2 = document.getElementById('password2');
const genderSelected = document.getElementById('select');
//Show input error messages
function showError(input, message) {
  const formControl = input.parentElement;
  formControl.className = 'form-control error';
  const small = formControl.querySelector('small');
  small.innerText = message;
}

//show success colour
function showSucces(input) {
  const formControl = input.parentElement;
  formControl.className = 'form-control success';
}

//check email is valid
function checkEmail(input) {
  const re = /^(([^<>()[]\.,;:s@"]+(.[^<>()[]\.,;:s@"]+)*)|(".+"))@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}])|(([a-zA-Z-0-9]+.)+[a-zA-Z]{2,}))$/;
  if (re.test(input.value.trim())) {
    showSucces(input)
  } else {
    showError(input, 'Email is not invalid');
  }
}


//checkRequired fields
function checkRequired(inputArr) {
  inputArr.forEach(function(input) {
    if (input.value.trim() === '') {
      showError(input, `${getFieldName(input)} is required`)
    } else {
      showSucces(input);
    }
  });
}


//check input Length
function checkLength(input, min, max) {
  if (input.value.length < min) {
    showError(input, `${getFieldName(input)} must be at least ${min} characters`);
  } else if (input.value.length > max) {
    showError(input, `${getFieldName(input)} must be les than ${max} characters`);
  } else {
    showSucces(input);
  }
}

//get FieldName
function getFieldName(input) {
  return input.id.charAt(0).toUpperCase() + input.id.slice(1);
}

// check passwords match
function checkPasswordMatch(input1, input2) {
  if (input1.value !== input2.value) {
    showError(input2, 'Passwords do not match');
  }
}

//check if selected a gender
function checkSelect(option) {
  if (select.value)
    showSucces(option);
  else
    showError(option, 'Please select a gender');
}



//Event Listeners
form.addEventListener('submit', function(e) {
  e.preventDefault();

  checkRequired([username, email, password, password2, genderSelected]);
  checkLength(username, 3, 15);
  checkLength(password, 6, 25);
  checkEmail(email);
  checkPasswordMatch(password, password2);
  checkSelect(genderSelected);
});

@import url('https://fonts.googleapis.com/css?family=Open+Sans&display=swap');
 :root {
  --succes-color: #2ecc71;
  --error-color: #e74c3c;
}

* {
  box-sizing: border-box;
}

.wrapper {
  width: 400px;
  max-width: 100%;
  box-sizing: border-box;
  padding: 25px;
  margin: 8% auto 0;
  position: relative;
}

.container {
  background-color: #fff;
  border-radius: 5px;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
  width: 400px;
}

h2 {
  text-align: center;
  margin: 0 0 20px;
}

.form {
  padding: 30px 40px;
}

.form-control {
  margin-bottom: 10px;
  padding-bottom: 20px;
  position: relative;
}

.form-control label {
  color: #777;
  display: block;
  margin-bottom: 5px;
}

.form-control input {
  border: 2px solid #f0f0f0;
  border-radius: 4px;
  display: block;
  width: 100%;
  padding: 10px;
  font-size: 14px;
}

.form-control input:focus {
  outline: 0;
  border-color: #777;
}

.form-control.success input {
  border-color: var(--succes-color);
}

.form-control.error input {
  border-color: var(--error-color);
}

.form-control small {
  color: var(--error-color);
  position: absolute;
  bottom: 0;
  left: 0;
  visibility: hidden;
}

.form-control.error small {
  visibility: visible;
}

.form button {
  cursor: pointer;
  background-color: #3498db;
  border: 2px solid #3498db;
  border-radius: 4px;
  color: #fff;
  display: block;
  padding: 10px;
  font-size: 16px;
  margin-top: 20px;
  width: 100%;
}

form {
  border: 0px solid black;
  display: inline-block;
  text-align: left;
}

body {
  margin: 50px 0px;
  padding: 0px;
  text-align: center;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  margin: 0;
  background-color: lightblue;
}

.nav {
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
  display: inline;
  resize: horizontal
}

label,
input[type="text,password,date"] {
  display: block;
  width: 150px;
  float: left;
  margin-bottom: 10px;
}

input[type="radio"] {
  display: block;
  width: 25px;
  float: left;
  margin-bottom: 10px;
}

label {
  text-align: right;
  width: 75px;
  padding-right: 20px;
}

br {
  clear: left;
}

h1 {
  color: black;
  text-align: center;
  font-size: xx-large;
}

.button {
  text-align: center;
  margin: auto;
  display: inline-block;
  padding: 5px 15px;
  font-size: 18px;
  cursor: pointer;
  text-align: center;
  text-decoration: none;
  outline: none;
  color: black;
  background-color: white;
  border: none;
  border-radius: 15px;
  box-shadow: 0 9px #999;
}

.button:hover {
  background-color: black;
  color: white;
}

.button:active {
  background-color: black;
  color: white;
  box-shadow: 0 5px #666;
  transform: translateY(4px);
}

p {
  font-family: verdana;
  font-size: 20px;
}

#wrapper {
  width: 30%;
  margin: 50px auto;
  padding: 50px;
  background: #D7FBFF;
}

.textInput {
  border: none;
  height: 28px;
  margin: 2px;
  border: 1px solid #6B7363;
  font-size: 1.2em;
  padding: 5px;
  width: 95%;
}

.textInput:focus {
  outline: none;
}

.btn {
  width: 98.6%;
  border: none;
  margin-top: 5px;
  color: white;
  background-color: #3b5998;
  border-radius: 5px;
  padding: 12px;
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
}

li {
  float: left;
  border-right: 1px solid #bbb;
}

li a {
  display: block;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

li a:hover:not(.active) {
  background-color: #111;
}

.active {
  background-color: #04AA6D;
}

output {
  display: inline;
}

.customizedBox {
  border: 1px solid #111;
  width: 500px;
  height: 400px;
}

select {
  width: 280px;
  height: 40px;
  padding: 10px;
  margin: auto;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  z-index: 1;
  border: none;
}

<div class="nav">
  <ul>
    <li><a href="HomePage.aspx">Home</a></li>
    <li><a href="MemesOverTheYears.aspx">Memes Over The Years</a></li>
    <li><a href="Profile.html">Profile</a></li>
    <li><a href="About.aspx">About</a></li>
  </ul>
</div>
<!-- partial:index.partial.html -->
<div class="wrapper">
  <div class="container">
    <form id="form" class="form">
      <h2>Register With Us</h2>
      <div class="form-control">
        <label for="username">Username</label>
        <input type="text" id="username" placeholder="Enter Username">
        <small>Error Message</small>
      </div>
      <div class="form-control">
        <label for="email">Email</label>
        <input type="text" id="email" placeholder="Enter email">
        <small>Error Message</small>
      </div>
      <div class="form-control">
        <label for="password">Password</label>
        <input type="password" id="password" placeholder="Enter password">
        <small>Error Message</small>
      </div>
      <div class="form-control">
        <label for="password2">Confirm Password</label>
        <input type="password" id="password2" placeholder="Enter password again">
        <small>Error Message</small>
      </div>
      <div class="form-control">
        <label for="gender">Gender</label> <br/>
        <select id="select">
          <option value="">Choose an option</option>
          <option value="Male">Male</option>
          <option value="female">Female</option>
          <option value="other">Other</option>
        </select>
        <small>Error Message</small>
      </div>
      <button type="submit">Submit</button>
    </form>
  </div>
</div>
<br /><br /><br /><br />
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