MediaKnight Download Denied Page

/**
 * Custom MediaKnight download denied page
 */

add_action( 'mediaknight_denied_download', function ( $attachment_id ) {

    ob_start( function ( $html ) {

        $request_uri = isset( $_SERVER['REQUEST_URI'] )
            ? wp_unslash( $_SERVER['REQUEST_URI'] )
            : '/';

        $login_url = wp_login_url( home_url( $request_uri ) );

        return '<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Login Required - [WEBSITE NAME]</title>
<style>
* {
    box-sizing: border-box;
}
body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    background: #172b46;
    color: #26364c;
    font-family: Arial, sans-serif;
}
.access-message {
    width: 100%;
    max-width: 560px;
    padding: 50px 35px;
    text-align: center;
    background: #ffffff;
    border-radius: 12px;
}
.access-message h1 {
    margin: 0 0 18px;
    color: #172b46;
    font-size: 32px;
}
.access-message p {
    margin: 0 0 25px;
    font-size: 17px;
    line-height: 1.6;
}
.access-message a {
    display: inline-block;
    padding: 13px 25px;
    background: #172b46;
    color: #ffffff;
    text-decoration: none;
    font-weight: bold;
    border-radius: 6px;
}
.access-message a:hover {
    background: #304d70;
}
</style>
</head>
<body>
<main class="access-message">
    <h1>Login Required</h1>
    <p>You must be logged in to your [WEBSITE NAME] account to download this file.</p>
    <a href="' . esc_url( $login_url ) . '">Log in to continue</a>
</main>
</body>
</html>';

    } );

}, PHP_INT_MAX );