I use a VPN for much of my internet access. It enables me to be in America for my Netflix account, be in England for my BBC online streaming and be anonymous for anything else. Recently I have found that if I choose to use a US server I cannot make any P2P connections. The connection appears normal but never connects to anyone else. Tonight I was pretending to be in Russia to watch the Rugby League on livestream and had the same problem.
It doesn’t matter at all, I can simply choose another server, Spain at the moment, and the problem is solved but I can’t find any hint of what is going on.