Notice: wp_enqueue_script was called incorrectly

You do not show how you hook your wp_enqueue_script() call.

But the error message you get is pretty clear, use one of the following hooks:

• wp_enqueue_scripts
• admin_enqueue_scripts
• login_enqueue_scripts

depending on the use case – see the notes at the wp_enqueue_script() codex page for additional information.

For example do for correctly enqueuing on the frontend:

function csv_three_script() {
    wp_enqueue_script(
        'csv3', 
        plugins_url( 
            '/js/demo.js', 
            __FILE__ 
        ), 
        array( 
            'jquery'
        )
     );
}
add_action( 'wp_enqueue_scripts', 'csv_three_script' );