After issuing su web7 you should check the auth.log again if there's everything ok. Using the command "who" you can view all logged in users on the system.
Same problem I had the same problem with ISPConfig 3.0.4.6: cron error with exit status 17 I found this thread and got a hint from someone mentioning /etc/passwd. So i checked it and found this: HTML: web3:x:5006:5007::/var/www/clients/client4/web3:/bin/false I had an account with working cron scripts, and it had this line: HTML: web4:x:5007:5006::/var/www/clients/client2/web4/./home/web4:/usr/sbin/jk_chrootsh So i changed the other one's home and shell and it worked right away. I still don't know what caused this, since I believe both accounts were created the same way.