Server and client behind routers

Hello
I have network:
Server and client1 in local network, client2 is remote. They all behind routers.

Server -- router1 ---------- Internet -----------router2 -- Client2
                         /
Client1 -- /

I have full epoptes connection Client1<>Server.

On router1 I did NAT -- Virtual Servers Setup:
External Port Start External Port End Protocol Internal Port Start Internal Port End Server IP Address
789 789 TCP/UDP 789 789 192.168.1.4

192.168.1.4 is server.
Similar thing I did on router2.

On client2:
$ sudo epoptes-client -c
depth=0 C = AU, ST = Some-State, O = Internet Widgits Pty Ltd
verify error:num=18:self signed certificate
verify return:1
depth=0 C = AU, ST = Some-State, O = Internet Widgits Pty Ltd
verify return:1

That stops at this point.
I have ssh and http access to client2.

I need help to move forward.