Form not submitting when enctype="multipart/form-data" is in tag

I have a form with text inputs and a file input all together. I need to include enctype="multipart/form-data" in the form tag (for the file), but when I do that my form doesn't even submit.

register.php

        <form method="post" name="registration_form" action="<?php echo esc_url($_SERVER['PHP_SELF']); ?>"  enctype="multipart/form-data">
        Instagram Username (DO NOT INCLUDE @): <input type='text' name='username' id='username' /><br>
        Team Name: <input type='text' name='teamname' id='teamname' /><br>
        Team Logo: <input type='file' name='logo' id='logo' /><br>
        Email: <input type="text" name="email" id="email" /><br>
        Password: <input type="password"
                         name="password" 
                         id="password"/><br>
        Confirm password: <input type="password" 
                                 name="confirmpwd" 
                                 id="confirmpwd" /><br>
        <input type="button" 
               value="Register" 
               onclick="return regformhash(this.form,
                               this.form.username,
                               this.form.email,
                               this.form.password,
                               this.form.confirmpwd);" /> 
    </form>

register.inc.php

if (isset($_POST['username'], $_POST['email'], $_POST['p'], $_POST['teamname'], $_POST['logo'])) {
// Sanitize and validate the data passed in
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$teamname = filter_input(INPUT_POST, 'teamname', FILTER_SANITIZE_STRING);

$target_dir = "logos/";
$target_file = $target_dir . basename($_FILES["logo"]["name"]);
$base = basename($_FILES["logo"]["name"]);
$name = pathinfo($base)['filename'];
$uploadOk = 1;
$imageFileType = pathinfo($target_file,PATHINFO_EXTENSION);
// Check if image file is a actual image or fake image
$check = getimagesize($_FILES["logo"]["tmp_name"]);
if($check !== false) {
    echo "File is an image - " . $check["mime"] . ".";
    $uploadOk = 1;
} else {
    echo "File is not an image.";
    $uploadOk = 0;
}
// Check if file already exists
if (file_exists($target_file)) {
echo "Sorry, file already exists.";
$uploadOk = 0;
}
// Check file size
if ($_FILES["logo"]["size"] > 500000) {
echo "Sorry, your file is too large.";
$uploadOk = 0;
}
// Allow certain file formats
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif" ) {
echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed.";
$uploadOk = 0;
}
// Check if $uploadOk is set to 0 by an error
if ($uploadOk == 0) {
echo "Sorry, your file was not uploaded.";
// if everything is ok, try to upload file
} else {
if (move_uploaded_file($_FILES["logo"]["tmp_name"], $target_file)) {
    echo "The file ". basename( $_FILES["logo"]["name"]). " has been uploaded.";
} else {
    echo "Sorry, there was an error uploading your file.";
}
}

$email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
$email = filter_var($email, FILTER_VALIDATE_EMAIL);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // Not a valid email
    $error_msg .= '<p class="error">The email address you entered is not valid</p>';
}

$password = filter_input(INPUT_POST, 'p', FILTER_SANITIZE_STRING);
if (strlen($password) != 128) {
    // The hashed pwd should be 128 characters long.
    // If it's not, something really odd has happened
    $error_msg .= '<p class="error">Invalid password configuration.</p>';
}
$prep_stmt = "SELECT id FROM members WHERE email = ? LIMIT 1";
$stmt = $mysqli->prepare($prep_stmt);

if ($stmt) {
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $stmt->store_result();

    if ($stmt->num_rows == 1) {
        // A user with this email address already exists
        $error_msg .= '<p class="error">A user with this email address already exists.</p>';
    }
} else {
    $error_msg .= '<p class="error">Database error</p>';
}
if (empty($error_msg)) {
    // Create a random salt
    $random_salt = hash('sha512', uniqid(openssl_random_pseudo_bytes(16), TRUE));

    // Create salted password 
    $password = hash('sha512', $password . $random_salt);

    // Insert the new user into the database 
    if ($insert_stmt = $mysqli->prepare("INSERT INTO members (username, email, password, salt) VALUES (?, ?, ?, ?, ?)")) {
        $insert_stmt->bind_param('sssss', $username, $email, $password, $random_salt);
        // Execute the prepared query.
        if (! $insert_stmt->execute()) {
            header('Location: ../error.php?err=Registration failure: INSERT');
            exit();
        }
    }
    if ($insert_stmtteam = $mysqli->prepare("INSERT INTO teams (name, logo, owner) VALUES (?, ?, ?)")) {
        $insert_stmtteam->bind_param('sss', $teamname, $name, $username);
        // Execute the prepared query.
        if (! $insert_stmtteam->execute()) {
            header('Location: ../error.php?err=Registration failure: INSERT');
            exit();
        }
    }
    header('Location: ./register_success.php');
    exit();
}
}