BIND9 : can't find domain.tld: No answer

My Bind9 server answers "No answer" to any query :

ychaouche@ychaouche-PC 12:11:02 ~ $ nslookup google.com 10.10.10.7
Server:         10.10.10.7
Address:        10.10.10.7#53

Non-authoritative answer:
*** Can't find google.com: No answer

ychaouche@ychaouche-PC 12:11:07 ~ $ nslookup facebook.com 10.10.10.7
Server:         10.10.10.7
Address:        10.10.10.7#53

Non-authoritative answer:
*** Can't find facebook.com: No answer

ychaouche@ychaouche-PC 12:11:11 ~ $ nslookup twitter.com 10.10.10.7
Server:         10.10.10.7
Address:        10.10.10.7#53

Non-authoritative answer:
*** Can't find twitter.com: No answer

ychaouche@ychaouche-PC 12:11:18 ~ $ 

Here's how it's configured.

root@dns2-sec 11:45:29 ~ # named-checkconf -p
options {
        directory "/var/cache/bind";
        listen-on-v6 {
                "any";
        };
        allow-query-cache {
                "any";
        };
        allow-recursion {
                "localnets";
                "localhost";
        };
        auth-nxdomain no;
        dnssec-validation auto;
        recursion yes;
        allow-query {
                "any";
        };
        allow-transfer {
                10.10.10.4/32;
        };
        also-notify {
        };
};
acl "ournets" {
        "localnets";
        192.168.200.0/24;
        192.168.201.0/24;
        192.168.202.0/24;
        192.168.203.0/24;
        192.168.204.0/24;
        192.168.205.0/24;
        192.168.206.0/24;
        192.168.207.0/24;
        192.168.208.0/24;
        192.168.209.0/24;
        192.168.100.0/24;
        192.168.101.0/24;
        192.168.102.0/24;
        192.168.103.0/24;
        192.168.104.0/24;
        192.168.105.0/24;
        192.168.106.0/24;
        192.168.107.0/24;
        192.168.108.0/24;
        192.168.109.0/24;
};
logging {
        channel "main_log" {
                file "/var/log/named/main.log" versions 3 size 2097152;
                severity info;
                print-time yes;
                print-severity yes;
                print-category yes;
        };
        category "default" {
                "main_log";
        };
        category "lame-servers" {
                "null";
        };
};
zone "algerian-radio.dz" {
        type slave;
        file "/etc/bind/slave/algerian-radio.dz.db";
        masters {
                10.10.10.4 ;
        };
};
zone "eprs.dz" {
        type slave;
        file "/etc/bind/slave/eprs.dz.db";
        masters {
                192.168.100.11 ;
        };
};
zone "10.10.10.in-addr.arpa" IN {
        type slave;
        file "/etc/bind/slave/10.10.10.in-addr.arpa.db";
        masters {
                10.10.10.4 ;
        };
};
zone "1.201.197.in-addr.arpa" IN {
        type slave;
        file "/etc/bind/slave/1.201.197.in-addr.arpa.db";
        masters {
                10.10.10.4 ;
        };
};
zone "10.16.172.in-addr.arpa" IN {
        type slave;
        file "/etc/bind/slave/10.16.172.in-addr.arpa.db";
        masters {
                10.10.10.4 ;
        };
};
zone "." {
        type hint;
        file "/etc/bind/db.root";
};
zone "localhost" {
        type master;
        file "/etc/bind/db.local";
};
zone "127.in-addr.arpa" {
        type master;
        file "/etc/bind/db.127";
};
zone "0.in-addr.arpa" {
        type master;
        file "/etc/bind/db.0";
};
zone "255.in-addr.arpa" {
        type master;
        file "/etc/bind/db.255";
};
root@dns2-sec 12:09:00 ~ # 

EDIT : seems to work fine with dig though, problem may come from nslookup ?

ychaouche@ychaouche-PC 12:21:13 ~ $ dig @10.10.10.7 twitter.com 

; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> @10.10.10.7 twitter.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29371
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;twitter.com.                   IN      A

;; AUTHORITY SECTION:
twitter.com.            84784   IN      NS      ns1.p34.dynect.net.
twitter.com.            84784   IN      NS      ns2.p34.dynect.net.
twitter.com.            84784   IN      NS      ns4.p34.dynect.net.
twitter.com.            84784   IN      NS      ns3.p34.dynect.net.

;; Query time: 0 msec
;; SERVER: 10.10.10.7#53(10.10.10.7)
;; WHEN: Tue Jun 07 12:23:21 CET 2016
;; MSG SIZE  rcvd: 126

ychaouche@ychaouche-PC 12:23:21 ~ $ nslookup  twitter.com 10.10.10.7
Server:         10.10.10.7
Address:        10.10.10.7#53

Non-authoritative answer:
*** Can't find twitter.com: No answer

ychaouche@ychaouche-PC 12:23:42 ~ $