Something's not working on your ACE server. It happens. This guide covers the most common problems and their fixes, roughly ordered by how often I see each one come up.
For general setup help, start with the Getting Started guide. For config-specific questions, the Configuration Guide is where you want to be.
Server Not Appearing in the Browser
This is the single most common issue people hit after first boot.
Wait a couple of minutes. It can take 1-3 minutes for a new server to register with the master server list. If you just started it, give it a moment before panicking.
Check that the server is actually running. Log into the LOW.MS Control Panel at control.low.ms and verify the server status shows as online. If it crashed during startup, it won't register at all.
Try direct connect. Use your server IP and port (found under Service Settings in the control panel) to connect directly. If direct connect works but the browser doesn't show your server, it's a registration delay – not a real problem.
Verify the server version matches your client. After a game update, the server needs updating too. Version mismatches will prevent the server from appearing in the browser entirely. Hit Steam Update in the control panel.
Players Can't Connect
If the server shows up but players get connection failures or timeouts:
Version mismatch – This is the culprit about half the time. Everyone needs to be on the same game version. After any ACE update, update your server immediately via the control panel.
Password typo – Sounds obvious, but double-check. Passwords are case-sensitive.
Server is full – If you've hit your maximum connections limit, additional players get rejected. Check your maxConnections setting. If you're running AI to fill slots, remember those count toward your total.
Firewall or network issues (self-hosted only) – If you're running your own hardware, verify that the required ports are forwarded correctly (likely TCP/UDP 9600 based on the ACC architecture, but check the official docs once v0.6 ships). LOW.MS servers have ports configured automatically.
Server Crashes on Startup
Check the Log Viewer for error messages. The most common causes:
Malformed JSON in config files. A missing comma, an extra bracket, an unescaped quote – JSON is fussy. Copy your config into an online JSON validator and it'll point to the exact line.
Invalid track or car references. If you specify a track folder name that doesn't exist, the server won't know what to load. Double-check spelling against the internal track names.
Corrupt server files. Run a Steam Update with validation to redownload and verify all server files.
If the logs don't make the problem obvious, try resetting to defaults. Rename your existing config files (don't delete them), restart the server so it generates fresh defaults, and then reapply your changes one at a time until you find which setting causes the crash.
Poor Performance and Lag
Players are reporting rubber-banding, teleporting cars, or general choppiness:
Too many connections for your hardware. Every connected player and every AI car adds CPU load. If you're running 30+ cars on modest hardware, that could be the limit. Reduce player count or AI count.
Network saturation. Sim racing sends a lot of positional data at high frequency. This is mainly a concern for self-hosters on residential connections.
Dynamic weather overhead. Switching to a static weather preset removes that processing load entirely.
High player-count AI. Running a 20-player server with 20 AI fill cars means simulating 40 cars. Keep the total car count within what your hardware can handle.
Client-side issues. If only one or two people are experiencing issues while everyone else is fine, the problem is on their end. Have them check their connection and try wired instead of WiFi.
Config Changes Not Taking Effect
Restart the server. Most configuration changes require a full restart.
Check you're editing the right file. If your server has a cfg/current/ directory alongside the main config files, the server may be reading from cached copies. Delete the current folder and restart.
Encoding issues. If your config was saved in UTF-8 instead of UTF-16 LE, the server might read values incorrectly or ignore them silently.
v0.6 AI Compatibility
The v0.6 update replaced ACE's AI track modelling system entirely:
- Community AI line files from v0.5 or earlier no longer work
- AI behaviour will be noticeably different – generally more aggressive
- Adjust the difficulty and aggression settings in your config rather than trying to use old AI data files
The new system is better, but existing AI tuning work needs to be redone from scratch.
Update and Version Issues
"Server version mismatch" errors – Update your server. On LOW.MS, click Steam Update in the sidebar.
Server won't start after update – Occasionally a major update changes config file format. Check patch notes, regenerate defaults if needed, and reapply customisations.
Rolling back – If a new update breaks something, use Cloud Restore to restore a pre-update backup while you sort out the new config requirements.
Getting Help
Check the Log Viewer first. Server logs almost always contain the information needed to diagnose issues.
Our support team is available 24/7 via live chat and email. When reaching out, include the relevant section from your server logs.
For the broader ACE community, the official Assetto Corsa Discord server has active channels for server administration discussion.