SQL-DATABASE ERROR

Database error in WoltLab Burning Board: Invalid SQL: SELECT userid, username, email, homepage, regdate, userposts, showemail, usercanemail, receivepm, lastactivity, uf.* LEFT JOIN bb1_userfields uf USING (userid) WHERE SUBSTRING(username,1,1) NOT IN ('A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z') AND activation=1 ORDER BY userposts DESC LIMIT 0,15
mysql error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LEFT JOIN bb1_userfields uf USING (userid) WHERE SUBSTRING(username,1,1) NOT IN' at line 1
mysql error number: 1064
Date: 20.05.2018 @ 13:45
Script: /memberslist.php?letter=%23&sortby=userposts&order=DESC&x=9&y=8&page=1
Referer: