if AD join works but authentication don't work try this from a ssh console:
squidclient -l 192.168.x.x -p 8080 -u YOURUSER -w YOURPASSWORD
http://www.google.comwhere -l is the firewall ip from green if you want to test from green, orange and so on..
-p the port where squid is listening to
-u the user you want to test
-w the user password
If doesn't work (it gives you an error), look permissions of: /var/cache/samba/winbindd_privileged
if you get permissions like this
drwxr-x--- 2 root root 4096 feb 04 13:18 winbindd_privileged
then this is the error because it should be owned by root:squid
To correct:
chown -R root:squid /var/cache/samba/winbindd_privileged
chmod -R 750 /var/cache/samba/winbindd_privileged
restartsquid --force