Unable to fetch correct query

There's a query that works as designed using MySQL. But trying to utilize MariaDB is doesn't seem to work. No visible error messages, it's as if the query isn't there.

The query fetches the "last reply" of a ticket, displaying the date/user. The last reply is calculated on the fly.

Link to discussion: http://www.blesta.com/forums/index.php?/topic/614-support-manager-last-reply/