Not being able to connect to server from different modem

[Obandowski]

I have created a server and client using the following tutorial:

https://wiki.apnictraining.net/_media/n ... pn_lab.pdf

The client and server were created in two Linux PCs with ubuntu 18.04. Both PCs were connected from the same network and the connection was working.

Once my client was connected from a different network I wasn't able to connect back to the server.

Any ideas on how to solve this issue?

Thanks in advance,