Increase Shield Security's 2FA timeout

functions.php

<?php
/**
 * Shield Security's 2FA timeout defaults to 5 minutes. This means that a user must
 * supply their 2FA code(s) within this time or they'll need to start again (re-login).
 *
 * Some email providers can be a bit slow at times with their email delivery, and 
 * 5 minutes isn't long enough. To provide a bit more time, you can use a filter to
 * extend the timeout to as many minutes as you need.
 *
 * Reference: https://support.getshieldsecurity.com/support/solutions/articles/3000101220
 */
add_filter( 'icwp-wpsf-login_intent_timeout', function () {
	return 10; // minutes. default: 5.
} );