Why can't some players connect to my multiplayer game?

Because the connection is failing at some stage: the server is down, overloaded, or unreachable; NAT/firewalls are blocking peer-to-peer connections (a classic 'can't connect to host' cause on home networks); matchmaking is failing to place the player; or there's a region/routing problem. Failures hitting some players (especially in P2P) suggest NAT issues; failures hitting everyone suggest server or matchmaking problems.

How do I fix NAT and connection issues in peer-to-peer multiplayer?

Implement NAT traversal so players behind restrictive home-network NATs can establish direct connections, and add a relay fallback for when direct connection still fails, so those players connect through a relay instead of being unable to join. NAT/firewall blocking is a major cause of P2P 'can't connect' failures, and traversal plus relay resolves most of it.

Why can't anyone connect to my game at launch?

That pattern, everyone unable to connect, points at server or matchmaking infrastructure: your servers are down, overloaded by the launch surge, or unreachable, or matchmaking is failing globally. Ensure your servers are up and have capacity (load-test before launch, since launch traffic often far exceeds testing), and that matchmaking handles the load. Universal connection failure is almost always an infrastructure or capacity problem, not a per-player one.

How to Fix Players Unable to Connect to Your Game

Quick answer: When players can't connect to your game, the connection is failing at some stage: the server is down or unreachable, NAT/firewalls block peer-to-peer connections, matchmaking fails to place the player, or there's a region/routing problem. Capture context about where and why connections fail, then address the specific stage, ensure server availability, add NAT traversal/relay for P2P, fix matchmaking, or provide regional servers.

Players unable to connect can't play at all, it's a complete barrier, and at launch a connection problem can sink the experience entirely. Connection involves several stages (reaching a server, matchmaking, establishing peer connections), and a failure at any stage blocks the player. Fixing it means finding which stage fails and addressing that specific cause.

Why Players Can't Connect

Connecting to a multiplayer game involves stages that can each fail. Server down/unreachable, if connecting requires reaching your server (matchmaking, authoritative server) and it's down, overloaded, or unreachable, no one can connect. NAT/firewall issues, for peer-to-peer connections, NATs and firewalls can block the direct connection between players (a classic cause of 'can't connect to host'), since many home networks don't allow unsolicited inbound connections without NAT traversal. Matchmaking failures, the matchmaking system fails to place the player (no match found, matchmaking service error). And region/routing issues, players in certain regions can't reach the server, or routing problems block them.

So 'can't connect' has multiple possible stages of failure, server reachability, NAT traversal, matchmaking, region, and the fix depends entirely on which one is failing for the affected players.

How to Diagnose It

Capture where and why connections fail, a connection-failure stage/error (couldn't reach server, NAT traversal failed, matchmaking returned no match, region error) is the key diagnostic. Look at the pattern: is it everyone (server down, a global matchmaking failure), specific players (NAT/firewall issues on their networks), specific regions (routing/regional server issues), or specific conditions (load)? Connection failures that hit some players but not others, especially in P2P, strongly suggest NAT/firewall problems; failures hitting everyone suggest server or matchmaking issues.

Bugnet captures errors and reported issues with context, so connection failures and their patterns surface, and server-side crashes/outages (which cause everyone to be unable to connect) show up in crash/monitoring data. Knowing whether failures are universal (infrastructure) or per-player (NAT) or regional is what tells you which cause to fix.

How to Fix It

Fix the failing stage. For server availability, ensure your servers (matchmaking, game servers) are up, have capacity (load-test for launch), and are reachable, server-down or overload is a common 'can't connect' cause, especially at launch. For NAT/firewall in P2P, implement NAT traversal (and a relay fallback for when direct connection fails), so players behind restrictive NATs can still connect, this is essential for P2P connectivity and resolves a large class of 'can't connect to host' failures. For matchmaking, fix the matchmaking failures (handle no-match-found gracefully, fix service errors). For regions, provide regional servers or fix routing so players everywhere can connect.

Also handle connection failures gracefully on the client, clear messaging about what failed and retry options, rather than a silent or cryptic failure. After fixing, verify players can connect across the conditions that were failing (different networks/NATs, regions, under load). Connection reliability is foundational, players who can't connect can't play, so addressing the specific failure stage (and load-testing connectivity before launch) is critical, especially for the launch surge.

Can't-connect fails at a stage: server down, NAT blocking, matchmaking, or region. Capture which, then fix server capacity, add NAT traversal/relay, or address matchmaking, load-test for launch.