Checkbox is not displaying when applying css

Hi Team

I have this code below, the issue with my checkbox are not displaying and there is not js file conflict when inspecting the element from the browser. What could be an issue? Please assist, thanks.

//css

#input[type=checkbox] {
    -webkit-appearance: checkbox;
    -moz-appearance: checkbox;
    appearance: checkbox;
}

// html and php

    
 Booking Courses
    
The courses available for booking or registration by the student.
    

        

            ping()) {
                die("Database connection failed.");
            }

            // Query to fetch available courses for the logged-in user
            $sql = "
            SELECT ac.course_id, ac.course_name, ac.duration, ac.category, ac.image
            FROM available_courses ac
            LEFT JOIN student_modules sm ON ac.course_name = sm.module_name AND sm.student_id = ?
            WHERE sm.student_id IS NULL";

            // Prepare the SQL statement
            $stmt = $conn->prepare($sql);
            if (!$stmt) {
                die("Error preparing the query: " . $conn->error);
            }

            // Bind the parameters
            $stmt->bind_param("i", $user_id); // Bind the user_id parameter

            // Execute the statement
            if (!$stmt->execute()) {
                die("Error executing the query: " . $stmt->error);
            }

            // Get the result
            $result = $stmt->get_result();
            if ($result === false) {
                die("Error fetching the result: " . $stmt->error);
            }

            // Check if courses exist for the logged-in user
            if ($result->num_rows > 0) {
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                echo '';
                while ($row = $result->fetch_assoc()) {
                    // Ensure image path is web-accessible
                    $imagePath = str_replace('C:/xampp/htdocs/', '/', htmlspecialchars($row['image']));

                    echo '';
                    echo '';
                    echo '';
                    echo '';
                    echo '';
                    echo '';
                    echo '';
                }
                echo '';
                echo '
Select
Image
Course Name
Duration
Category
' . htmlspecialchars($row['course_name']) . '
' . htmlspecialchars($row['duration']) . '
' . htmlspecialchars($row['category']) . '
';
            } else {
                echo '
No courses available at the moment.
';
            }

            // Close the statement and the connection
            $stmt->close();
            $conn->close();
            ?>
        
        Register