ssh: connect to host 192.168.43.91 port 22: Connection refused code example
Example: ssh: connect to host 192.168.178.45 port 22: Connection refused lost connection
Your ISP may block connections to port 22 (nothing you or your router can do about it). Just set SSHd to run on a different port, e.g. 2222.
In /etc/ssh/sshd_config, change Port 22 to Port 2222 and then sudo service ssh restart. Port forward 2222 (or whatever), and try again.