How to Fix Connection Errors in Slay the Spire 2

Slay the Spire 2 is the highly anticipated sequel to the genre-defining roguelike deckbuilder, bringing fresh characters, deeper mechanics, and online co-op for up to four players. The co-op mode has quickly become a fan favorite, turning a beloved solo experience into something even better with friends.

However, multiplayer isn't always smooth. The game uses peer-to-peer connections, and many players encounter connection failures, lag spikes, desync errors, or endless searching. Most don't know what's causing it or how to fix it. This guide breaks down the common issues and gives you practical solutions.

Why Do P2P Games Also Fail to Connect?

Many players assume that since Slay the Spire 2 uses peer-to-peer connections, multiplayer should be more stable, no server middleman, no server downtime, direct player-to-player link. But in practice, P2P connections can be just as fragile, sometimes even more so. Here's why:

• NAT type conflicts — Many home routers use strict NAT settings that block direct connections between players, making it impossible for peers to find each other.
• Host network quality — In P2P, the host's connection carries the session. If the host has unstable internet, everyone in the party feels it.
• Geographic distance — The farther apart players are, the more routing hops the connection passes through, increasing latency and packet loss.
• Firewall and port blocking — Security software or router firewalls can silently block the ports needed for P2P communication, causing connection failures without any clear error message.
• ISP routing issues — Different internet service providers use different routing paths. Some routes between ISPs are inefficient or congested, causing drops even when both players have fast internet.

In short, P2P doesn't mean "plug and play." Without a stable network on both ends, connection problems are almost guaranteed.

Common Connection Issues

When multiplayer goes wrong in Slay the Spire 2, the symptoms are usually obvious. You might not see your friends online even though you're both connected. Joining a lobby can get stuck on an endless loading screen. Sometimes the game goes black after connecting with no way to proceed. Other times you connect successfully only to get kicked back to the menu within seconds. These issues can happen individually or pile up together, and most of them trace back to the same root causes: NAT conflicts, firewall blocking, or unstable routing between players.

How Can You Fix Slay the Spire 2 Connection Errors?

Boost Your Connection with GearUP

GearUP’s strength lies in its optimization of NAT and network nodes. Simply put, NAT improves your connection visibility, and nodes optimize data transmission paths, which helps minimize issues like your friends list not showing other players or experiencing lag in Slay the Spire 2.

GearUP

GearUP’s network optimization works in real time. Its dynamic multi-path routing continuously analyzes game traffic and public network conditions to handle sudden network jitter, which is crucial for online play unless you don’t mind disconnecting at critical moments. If you’d like to try it, you can follow the process below:

1. Search for Slay the Spire 2, click the arrow or click "Boost" to start accelerating.
   
2. Keep GearUP running in the background — it will continuously provide network optimization, then launch the game.
   

※ For best results, both players should enable GearUP.

Let the Most Stable Player Host

In Slay the Spire 2, the host's connection carries the entire session. Follow these steps:

• Have each player run a speed test and compare results.
• Choose the player with the lowest ping and most consistent upload speed.
• That player creates the room and invites others.

Enable UPnP on Your Router

UPnP allows the game to automatically open the ports needed for Slay the Spire 2 communication.

1. Open a browser and type your router's IP address (usually 192.168.1.1 or 192.168.0.1).
2. Log in with your router's admin credentials.
3. Look for UPnP under Advanced Settings or NAT Settings.
4. Turn it On and save.
5. Restart your router and try connecting again.

Make Sure Your Firewall Isn't Blocking the Game

Windows Firewall or third-party security software can silently block the game's network traffic.

1. Open Windows Security → Firewall & network protection.
2. Click Allow an app through firewall.
3. Look for Slay the Spire 2 in the list. If it's not there, click Allow another app and browse to the game's installation folder.
4. Make sure both Private and Public boxes are checked.
5. Click OK and relaunch the game.

Use a Virtual Network Adapter

If the above methods don't work, a virtual network adapter can help bypass NAT restrictions and ISP routing issues.

1. Download and install GearUP.
2. Open the app and search for Slay the Spire 2.
3. Select the game and click Boost.
4. GearUP will create an optimized virtual connection between players, reducing the impact of strict NAT types and poor ISP routing.
5. Launch the game and try connecting again.

This is especially helpful when playing with friends in different regions.

Slay the Spire 2 Connection Failures FAQ

Q1: Why does the connection fail when I'm the host?
A: This may be because your NAT is poor or your network is unstable. Have a player with a more stable network act as the host.

Q2: Can a VPN solve this problem?
A: Unlikely. A VPN does not aim to optimize the best connection path; its purpose is to mask your IP address, so it not only fails to improve connection stability but may also cause high latency.

Q3: Is faster internet speed better?
A: Internet speed has little impact on connection stability; you should focus more on stability and NAT.

Conclusion

Many players mistakenly focus on internet speed or game settings when dealing with Slay the Spire 2 connection failures, overlooking network stability and connection visibility issues, which leaves the problem unresolved. By following the methods in this article, using GearUP’s optimizations and making adjustments to your local network, you are very likely to avoid connection failures and enjoy a better gaming experience.