Can't Join an ATS Convoy Server? Fix DLC, Mod and Version Errors

When drivers cannot join an American Truck Simulator Convoy dedicated server, the cause is almost always a mismatch: their active DLC or mods differ from the server packages, their game version differs from the server's, or (if you raised the player cap) their g_max_convoy_size is lower than the server's. When the server does not show in the session list at all, search for it by its search ID from the server console instead of by name, and check the console for errors like "Server packages file not found".

Work through the checks below in order. The first three fix the large majority of cases.

How the server decides who can join

The ATS dedicated server never loads DLC or mod files. It reads server_packages.sii and server_packages.dat, two files exported from the host's own game, which describe the exact map DLC, mods and mod order the session uses. Every driver who joins has to match that description. The game version has to match too. Anything that differs, and the join fails or the session is filtered out of the list.

Check 1: Active DLC matches the packages

The common case: the host exported packages from a profile with Oregon, Washington, Utah and Texas active, and one friend owns only the base game or has a state unticked.

• Owned is not the same as active. The DLC has to be enabled for the game. In your Steam Library, right click American Truck Simulator, open Properties > DLC and make sure each state is ticked. A DLC unticked there is invisible to the game.
• Ask what the session needs. Click the session in the Convoy browser. The panel on the right lists what it requires.
• Export from the common set. If one driver lacks a state, re export the packages from a profile with only the DLC everyone owns. This is the cleanest fix for a regular group.

The ATS base map (California, Nevada and Arizona) needs no DLC. A base game package lets anyone with the game join.

Check 2: Mods and mod order match

Mods must match exactly: same mods, same versions and the same load order.

1. In the Convoy browser, select the session. Sessions that use mods show them in the right hand panel.
2. Use Activate Session MODs if it appears. The game offers to subscribe to the host's Steam Workshop mods and reorder your list to match.
3. For mods from outside the Workshop, everyone needs the same file from the same source. A renamed or edited copy counts as a different mod.
4. After a Workshop mod updates, the server packages are out of date. The host re exports and re uploads, and players let Steam finish downloading the update. If one person has a stale version, unsubscribing and resubscribing forces a fresh copy.

If you want drivers to be able to join with or without cosmetic mods, set mods_optioning: true in server_config.sii. That only applies to mods their authors have flagged as optional for multiplayer; map and truck mods stay mandatory.

Check 3: Everyone is on the same game version

After an ATS patch, the server and every player must be on the same version. Two traps:

• The server has not updated yet. A dedicated server only updates when it is reinstalled or restarted with an update step. Restart it after every patch and check the version it reports when it starts.
• Someone is on a beta branch. SCS runs open betas before most big updates. A player who opted into the beta in Steam (Properties > Betas) is on a newer version than a public branch server and cannot join it. Switch back to None and let Steam download.

Check 4: The server does not show in the session list

Without a logon token, the server signs in anonymously and gets a new search ID every time it starts, so the ID from last week's convoy no longer works. Tokens are made at steamcommunity.com/dev/managegameservers with the game's app ID 270880.

Check 5: You raised max_players above 8

SCS supports 8 drivers per session. Since update 1.50, groups have been raising max_players on the server, which is unsupported. If you do, there is a catch: every driver must also raise g_max_convoy_size in their own Documents\American Truck Simulator\config.cfg to at least the server's value. Drivers who skip this cannot find the server. If only some of your group can see the session, this is the first thing to check.

Check 6: Read the server log

The console and server.log.txt in the server's home folder name the problem directly. Lines worth knowing, from the SCS documentation:

<ERROR> [MP] Error: Server packages file not found. This is required to load proper map, DLCs and mods

The packages are missing or in the wrong folder. They belong next to server_config.sii in the server's home folder (~/.local/share/American Truck Simulator on Linux).

[MP] Steam disconnected
[MP] Session closure requested (reason - 33)

The server lost its connection to Steam: a network drop or, on a home PC, sleep mode. Turn off sleep on any machine that hosts a convoy.

[S_API FAIL] SteamAPI_Init() failed; unable to locate a running instance of Steam

On Linux, the server cannot find the Steam client library. The steamclient.so file needs to be in ~/.steam/sdk64.

Check 7: The player's own network

Since version 1.46, Convoy drops players whose network blocks inbound UDP traffic. A driver who connects and is kicked a few minutes later, or never finishes joining, should check that their router or firewall is not blocking UDP. Players do not need to forward ports, but strict firewalls, some VPNs and some workplace or school networks cause exactly this. The general error players see is "An error occurred while connecting to the session", which can mean any of the checks above, so work down the list.

A short checklist to share with your drivers

1. Game updated, not on a beta branch.
2. Every DLC state in the session ticked in Properties > DLC.
3. Mods matched with Activate Session MODs, same order as the host.
4. Join by search ID.
5. If the server has more than 8 slots, g_max_convoy_size raised in config.cfg.

The full setup, including exporting the packages, is in our ATS convoy server guide. If your group also plays ETS2, its mod workflow is in adding mods to a Euro Truck Simulator 2 convoy server.

Skipping the server side problems

A GamezServers ATS server removes the host side of this list. We create the Steam logon token when the server is set up, so the search ID stays the same after every restart, the server checks for game updates when it starts (a restart from the panel after a patch is enough), and there is no PC that can fall asleep mid convoy. Packages and server_config.sii go up through the file manager or SFTP, and the live console shows the search ID and any package errors. The DLC and mod matching on the drivers' side still applies to every convoy server.

FAQ

Why can my friend not join my ATS convoy when they own the DLC?

The DLC must be active in Steam (Properties > DLC) and in the profile they join with. Owning it is not enough, and their mods and mod order must match the server packages too.

Why does my ATS convoy server have a different search ID every day?

The server is running without a Steam logon token, so it signs in anonymously and gets a new ID each start. Add a token to server_logon_token in server_config.sii.

Do I need to re export server packages after a mod update?

Yes. The packages describe the mod versions at the time of export. After an update, export again from your game and upload the new server_packages.sii and server_packages.dat.

Can players on the ATS beta join a normal server?

No. A beta client is a different version. They need to switch back to the public branch, or the whole group and the server need to move to the beta together.