Your Fastweb home connection seems to give you an IPv6 IP address, with (what seems to be) no IPv4 backwards compatibility. So, with that connection, you cannot reach websites/servers that do not support IPv6... which means you can basically only reach around 22% of the entire Internet:
https://www.google.com/intl/en/ipv6/statistics.html
While you were on your mobile network, you had a working IPv4, which is why you were able to connect to the server.
Our MU server does not support IPv6 connections, so you cannot play while having an IPv6 IP address.
You could try disabling IPv6 on your end, and see if by doing so, you will force Fastweb to assign an IPv4 IP address to your connection:
https://support.purevpn.com/how-to-d...pv6-on-windows