WP_User_Query with 2 sets of conditions ‘AND’

You have an example here: https://codex.wordpress.org/Class_Reference/WP_User_Query#Custom_Field_Parameters

Problem with your query is that you use wrong keys. It should be:

$args = array (
    'meta_query' => array(
        'relation' => 'AND',
        array(
            'key' => $campaign_type, 
            'value' => $Campaign_ID,
            'compare' => '='
        ),
        array(
            'key' => 'organisation',
            'value' => $userOrg,
            'compare' => '='
        )
));

Longer versions (meta_key, meta_value, meta_compare) are used, when you don’t use meta_query but put them directly in the query.