Troubleshooting - AutoModpack

This page explains the messages AutoModpack shows when a join or an update fails. Each entry says what the message means and which side fixes it. The screens a player sees in normal use, including the "Modpacks" screen and its actions, are described in For players. If a message is not on this page, the log usually holds the details.

Join disconnect reasons

When a join cannot continue, the server ends the login and the game shows the reason on the disconnect screen. A few reasons carry a version or a loader name, so the table quotes the part of each message that stays the same.

Message	What it means	Who fixes it
`[AutoModpack] Install/Update modpack to join`	The client just installed or updated the modpack, and the change needs a game restart.	Player: close the game, start it again, and join again.
`Install the AutoModpack mod to get this server's modpack!`	The player joined without the AutoModpack mod, and this server requires it. This text is the server's `nag-message` setting, so it can differ.	Player: install the mod. Admin: check `require-modpack` in the server config.
`This server does not accept your mod loader. Join with`	The player joined with a loader the server does not accept, for example Forge on a Fabric server. The message names the loader to use.	Player: join with that loader.
`AutoModpack version mismatch. This server runs`	The player's AutoModpack version differs from the server's. The message names the version to install and the loader to install it for.	Player: install that AutoModpack version from Modrinth.
`AutoModpack is generating modpack. Please wait a moment and try again.`	The server is publishing a generation at this moment, so there is nothing to serve yet.	Player: join again in a moment.
`You are not authorized to join this server!`	The login did not pass the server's identity checks, such as the whitelist or a ban.	Admin: check the whitelist and the bans. Players ask the admin.
`[AutoModpack] Your client stopped this connection: the server's certificate does not match the certificate saved for this server.`	The server presented a certificate that does not match the pin saved on the client.	Both: see certificate mismatch.
`[AutoModpack] Certificate verification was dismissed. Reconnect and verify the certificate to join.`	The player closed the certificate verification screen without deciding.	Player: reconnect and accept or skip.
`[AutoModpack] Join cancelled.`	The player backed out during the optional modpack offer.	Player: join again when ready.
`[AutoModpack] Host server error. Please contact server administrator to check the server logs!`	The client could not use the pack host the server advertised, or answered with something the server did not expect.	Admin: read the server log. Start at reading the join logs.
`[AutoModpack] Your modpack verification response was unreadable.`	The server failed to read the client's answer. The connection dropped or the client is broken.	Player: reconnect. Admin: check the log if it repeats.
`[AutoModpack] The server failed to process your handshake.`	The server hit an error while checking the login.	Admin: check the server log.
`AutoModpack modpack hosting is unavailable on the server.`	The server advertises the default `HOLEPUNCH` mode, but its modpack host never came up.	Admin: check the server log and the hosting setup.

The error screen

When AutoModpack fails and cannot continue, it shows its own screen with the title Something went wrong!. The screen names a category and shows one sentence about the failure. The categories and their usual meaning:

Category	What it usually means	What to do
Connection	AutoModpack did not connect to the modpack host.	Check that the server is up and that the address is right.
Server content	AutoModpack did not read the server modpack.	Contact the server operator.
Invalid local data	AutoModpack found invalid local modpack data.	Try `Retry` first. If it repeats, report it with the log.
Update	AutoModpack did not apply the modpack update.	Try `Retry`. If it repeats, report it with the log.
Local storage	AutoModpack did not update its local storage.	Try `Retry`. If it repeats, report it with the log.
Security	A certificate pin input was invalid, for example a mistyped pinned address.	Paste the complete address the operator gave you.
Unexpected error	AutoModpack ran into a problem it did not expect.	Report it with the log.

The screen has up to four buttons:

Retry starts the failed step again. It appears only when the step can be retried.
Open logs opens the log folder, so the log is at hand.
Copy details copies the diagnostic text to the clipboard, and a green Copied note appears at the top of the screen. Paste the details into a bug report.
Back closes the screen.

The screen also says that the full diagnostic details are in the log file.

Restart reasons

When an update closes the game, the restart screen lists its reasons under Restart needed because:. The lines are plain sentences. The less obvious ones:

Screen line	What happened
`The launcher Minecraft version changed`	The pack runs a different Minecraft version than the instance.
`The launcher modloader changed`	The pack runs a different mod loader, for example Fabric instead of Forge.
`The mod loader version changed`	The mod loader version changed.
`Mods were copied into the standard mods directory`	The update placed mods in the standard `mods` folder, where only a restart loads them.
`Nested mods were unpacked into the standard mods directory`	A mod that ships another mod was unpacked, and the copies need a restart to load.
`Duplicate mods were removed`	The same mod existed twice, and the extra copy was removed.
`Mods that do not belong to the modpack were removed from the standard mods directory`	Mods outside the pack were removed so they cannot conflict with it.
`Your local mods were kept on the instance timeline`	The player approved keeping own mods. They moved to the instance timeline, out of the game directory.
`Your group selection changed`	The optional parts of the pack the player picked changed which mods load.
`The selected modpack changed`	The player switched to a different pack on the same server.
`Set this instance to Minecraft %s (%s) in your launcher before the next start`	The pack needs a different game version or loader, and the launcher manages them. The player sets both in the launcher. The screen fills in the Minecraft version and the loader with its version.

The server side

The same failures leave their mark in the server log. When a join fails, the log line names the player and the reason. The page reading the join logs lists the lines to look for. To watch downloads live, run host activity on the server, described in commands.

Where are the logs

The client and the server both log to the standard Minecraft log, latest.log, in the logs folder. When the detached update helper runs, it writes its own report to automodpack/helper/last-helper-run.log. The FAQ covers the log locations in short.