Ok, I've confirmed it's time_too_late being NULL causing it. I removed that check and it was able to find mailer queues to send. The query is as follows, which you can run directly on your database
Code:
SELECT m.*
FROM `TABLE-PREFIX-HERE_cbsubs_mailer_mailqueue` AS m
WHERE m.`state` = 'A'
AND m.`time_to_mail` <= '2017-12-05 13:53:46'
AND m.`time_too_late` > '2017-12-05 13:53:46'
ORDER BY m.`priority` DESC, m.`time_to_mail`
LIMIT 0, 100
.
Remove the time_too_late check and it'll find results. I don't think time_too_late is actually supposed to be NULL. Best I can suggest is as a workaround is to run an update query to set time_too_late to time_to_mail if NULL. Example as follows.
Code:
UPDATE `TABLE-PREFIX-HERE_cbsubs_mailer_mailqueue` SET `time_too_late` = `time_to_mail` WHERE `time_too_late` IS NULL
I've added a bug ticket to further look into this.
#6906