sshd active (listening), ssh packets incomming, but sshd not answering

1) I'm on Centos 7.X (latest), KVM VM, on www

2) The VM has two interfaces internal (10.0.0.X, eth0) and external (176.y.y.y, ens7).

3) I've a vanilla sshd configuration (that is, it listen on all interfaces/ips)

4) If I ssh on the VM from the www, I can trace (tcpdump -i ans7 ....) the incoming ssh packets

5) With ss -nlput I get (I delete white space to get the result of the command on a single line)

[...]
tcp   LISTEN     0      128    *:22   *:*   users:(("sshd",pid=1494,fd=3))
[...]

6) I rebooted, I restarted the services, but ssh does not work from www (only from the internal network 10.0.0.1/24) and with tcpdump I see that there are no returning ssh-packets.

I have spent more that one hour on a task that I've done 100 times, but I have no idea where to look now.

EDIT Also ping does not work, probably it is a network problem.