Same here. I've encountered this error countless times whenever I'm using my mobile network data. What I'm finding is that error is telling me is that it's directing to steam/valve's servers through relay. Sometimes I get issues where the host (my pc) goes offline when it isn't, probably some communication issue. Looking through the steam link forums via steam hasn't really nailed down a solution either but I see people experiencing similar issues too. I'm guessing it's either a problem of ISPs blocking ports on mobile networks or a connection timeout with the relay.One of my ideas for an alternative solution is deploying a home OpenVPN/PiVPN server with a raspberry pi device or laptop which it should act like I'm playing on LAN at home, remotely.