postgresql sub query

Question

I have three tables

1. kit - contains kit_id and kit_type (kit type is with android or IOS)
2. appointment - contains appointment_id, created_datetime, kid_id, created_by_id
3. user - contains user_id, user name, email etc

I am trying to get the number of appointments used by each kit within a certain date range which I can do with a group. But I also want to extract the user details of the person who last used the kit - note each kit can have multiple users and be used for multiple appointments. I have tried to use subqueries but keep ending up with a higher count probably related to my joins.

The first part without subquery is

select k.kit_id, u.user_first_name , u.user_last_name , u.user_email  ,count(*) as number_of_rows from tbl_appointment a 
join tbl_kit k on k.kit_id =a.kit_id 
join tbl_user u on a.created_by_user_id  = u.user_id 
where a.created_datetime >'2023-07-01 00:00:00.000'
and a.created_datetime > '2023-08-01 00:00:00.000'
and k.kit_type_code ='ANDROID'
and (k.kit_is_blocked = '0' or k.kit_is_blocked is null)
group by k.kit_id,u.user_first_name,u.user_last_name , u.user_email  
order by number_of_rows desc

But this could be joining on any user and not necessarily the most user of the most recent appointment

The following is an example of what I have tried but it is wrong. If someone could tell me whats wrong I would be very grateful - note only trying to get created_by_user_id as once i have that joining to user table should be easy

SELECT
    a.created_by_user_id,
    k.kit_id,
    count(*) AS number_of_rows
FROM tbl_appointment a
JOIN tbl_kit k ON k.kit_id = a.kit_id
LEFT JOIN (
    SELECT
        a.kit_id,
        MAX(a.created_datetime) AS most_recent_created_datetime
    FROM tbl_appointment a
    WHERE a.created_datetime > '2023-07-01 00:00:00.000'
    AND a.created_datetime < '2023-08-01 00:00:00.000'
    GROUP BY a.kit_id
) most_recent ON k.kit_id = most_recent.kit_id
LEFT JOIN tbl_user u ON most_recent.most_recent_created_datetime = a.created_datetime
WHERE k.kit_type_code = 'ANDROID'
AND (k.kit_is_blocked = '0' OR k.kit_is_blocked IS NULL)
GROUP BY a.created_by_user_id, k.kit_id
ORDER BY number_of_rows DESC;