# Troubleshooting

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](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](configuration/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](https://modrinth.com/mod/automodpack). |
| `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](security#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](how-it-works/hosting#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](how-it-works/hosting). |

## 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](how-it-works/hosting#reading-the-join-logs) lists the lines to look for. To watch downloads live, run `host activity` on the server, described in [commands](commands#hosting).

## 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](faq#where-are-the-logs) covers the log locations in short.