gdpr_strictly_enabled_category not working (Polylang setup)

Acocrding to this page https://www.webtoffee.com/modify-strictly-enabled-cookie-categories-using-webtoffee-gdpr-cookie-consent-plugin/
This is how you add strictly enabled cookie categories. However, it is not doing anything.
Has the function been changed or is it not compatible with polylang?

function webtoffee_strictly_enabled_cookie_categories($strict_categories) {

    $count = count($strict_categories);
    $strict_categories[$count] = 'notwendig';

    return $strict_categories;
}

add_filter('gdpr_strictly_enabled_category', 'webtoffee_strictly_enabled_cookie_categories');

Yes, the functions.php is working otherwise

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