Cannot connect to world - xbox live

No one can connect to my world using xbox live unless they are in the same network as I (see attached image). So, for example, my son, in another house, cannot connect to my world but I can connect to his.

Maybe it has something to do with my router. I've tried to port forward some ports used by xbox live but maybe I missed something. I don't know 🙁 To rule that out I've enabled Game Mode in the router (see attached image). No success.

I've searched the forum but I found no solution that worked.

Any ideias?