sign in and logout scrpit not working, however, signup script is working perfectly fine

i have an index.php file...in which there is the sign in form and a seperate signup file after sign up....it shhould be redirected to index.php... whereby once sign up-ed...the login form inside the index.php should not appear...only the logout button...however, both is not working(sign in and logout) please help. thanks

here is my logout scrpit:

<?php

session_start();

session_unset();

session_destroy();

header("Location: index.php");

and here is my sign in scrpit:

<?php


if (isset($_POST['login-submit'])) {

require 'dbh.inc.php';

$mailuid = $_POST['mailuid'];
$password = $_POST['pwd'];

if(empty($mailuid) || empty($password)) {

    header("Location: ../index.php?error=emptyfields");
    exit();
}
else{

    $sql = "SELECT * FROM users WHERE uidUsers=?; ";
    $stmt = mysqli_stmt_init($conn);

    if (!mysqli_stmt_prepare($stmt, $sql)) {
        header("Location: ../index.php?error=sqlerror");
        exit();
    }
    else{
        mysqli_stmt_bind_param($stmt, "s", $mailuid);
        mysqli_stmt_execute($stmt);
        $result = mysqli_stmt_get_result($stmt);

        if ($row = mysqli_fetch_assoc($result)) {
            $pwdCheck = password_verify($password, $row['pwdUsers']);
            if ($pwdCheck == flase) {
                header("Location: ../index.php?error=wrongpassword");
                exit();
            }
            else if($pwdCheck == true) {
                session_start();
                $_SESSION['userId'] = $row['idUsers'];
                $_SESSION['userUid'] = $row['uidUsers'];

                header("Location: index.php?login=success");
                exit();
            }

            else{
                header("Location: ../index.php?error=wrongpassword");
                exit();
            }
        }
        else{
            header("Location: ../index.php?error=nouser");
        exit();
        }
    }
}
}
else{
header("Location: ../index.php");
    exit();
}