Why isn't traffic going to the server?

Question

iptables

Good morning, the problem is as follows:
There is a server that is behind the Zyxel Keenetic Giga router, apache is installed on the server, from the internal network, the site opens at an external address, from outside the site is not available.

[[email protected] ~]# netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      2181/master
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      2213/mysqld
tcp        0      0 0.0.0.0:5038            0.0.0.0:*               LISTEN      3269/asterisk
tcp        0      0 0.0.0.0:110             0.0.0.0:*               LISTEN      997/dovecot
tcp        0      0 0.0.0.0:143             0.0.0.0:*               LISTEN      997/dovecot
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      981/sshd
tcp6       0      0 ::1:25                  :::*                    LISTEN      2181/master
tcp6       0      0 :::110                  :::*                    LISTEN      997/dovecot
tcp6       0      0 :::143                  :::*                    LISTEN      997/dovecot
tcp6       0      0 :::80                   :::*                    LISTEN      974/httpd
tcp6       0      0 :::22                   :::*                    LISTEN      981/sshd

[[email protected] ~]# iptables -L -n
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:22
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:80
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpt:5060
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpt:5061
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:5060
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:5061
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpts:10000:20000
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpt:4569
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:5038

Chain FORWARD (policy DROP)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Answer 1

ISP is blocking incoming connections on port 80

Answer 2

Have you looked at tcpdunp? Does the traffic come to the server at all?
Maybe the router is not letting through?