cron.job_run_details is still empty

Hi
I have installed /configured pg_cron for may database aps . I have scheduled some jobs like :
aps=> SELECT cron.schedule('0 10 * * *', 'VACUUM');
schedule
----------
1
(1 row)
and
aps=> select * from cron.job_run_details order by start_time desc limit 5;
jobid | runid | job_pid | database | username | command | status | return_message | start_time | end_time
-------+-------+---------+----------+----------+---------+--------+----------------+------------+----------
(0 rows)
the pg_cron table is always empty