Trigger User Switch

Hi there, I am trying to add a user switching dropdown menu to the wordpress admin toolbar.

$nonce_url = wp_nonce_url(site_url().'/wp-login.php?action=switch_to_user&user_id='.$user->ID);

however when I click on it, I get wordpress failure notice,
Are you sure you want to do this?
Please try again.

https://ww.wp.xz.cn/plugins/user-switching/