Direct answer

Confirm both the client main menu and running server log show 42.20.4. Stop the instance, update the actual install directory, restart, and read the new startup string before touching mods or saves. If exact builds match, move to file integrity and Workshop diagnostics without disabling Lua checksum protection.

Do this first

  1. Capture the client's full main-menu version.
  2. Stop the server and read its last startup version and launch path.
  3. Update and validate the exact directory the service launches.
  4. Restart and confirm both sides show 42.20.4.
  5. Only then isolate base-game files, Workshop content, and OS-specific file errors.

Version first, files second

A connection failure or file mismatch can come from different game builds, different mod content, or local file changes. Exact client/server version equality is the cheapest fact to establish first. Current Stable is 42.20.4; a server that still logs 42.20.3 is outdated even if its control panel says restarted.

The wrong install can update cleanly

SteamCMD can report success for one directory while a service launches another. Compare configured launch and update paths, then use the server startup log as the result.

  • Stop the instance.
  • Confirm install and launch directories.
  • Update and validate the correct installation.
  • Restart and read the new version.

ISReadABook.lua or files do not match

A fresh 42.20.4 report names ISReadABook.lua after clients and servers updated. Because the evidence is still community-level, do not copy files between machines or turn off Lua checksum as a first response. Verify both installations, remove local edits, test a clean vanilla client, and record operating systems plus the exact file named in both logs.

  • Matching version strings
  • Verified base-game and dedicated-server files
  • No local script edits
  • Disposable vanilla connection
  • Client and server logs from the same attempt

When versions match

Move to Workshop item versions, dependencies, file integrity, and the joining-game diagnostic. Keep checksum and security settings enabled; weakening them can hide the mismatch and undo the protection added by the hotfix.

FAQ

Quick answers

Why does SteamCMD say updated while the server is old?

It may have updated a different install. Verify the path the running service launches and read its startup log.

Should I disable Lua checksum to join?

No. Match builds and verify files first. Disabling a security check can hide the cause and is especially inappropriate after a security hotfix.

What if ISReadABook.lua still does not match?

Preserve both logs, verify clean files on both sides, note each operating system, and report the reproducible vanilla case rather than copying community files blindly.

Evidence log

Sources checked

Official sources establish universal facts; forum and specialist sources are used for symptoms, vocabulary, and cross-checking.

Official42.20.4 Stable Security Hotfix

Official 26 August security hotfix for Stable 42.20.4, beta 42.19.2, and legacy41 41.78.21, including removal of loadstring and loadstream.

Official forumUnable to Join Server: Stuck at Loading

Current Steam support-language evidence for 42.20.x dedicated servers that remain on an older build after a client update.

Official forumBuild 42 File Does Not Match Report

Support report showing version mismatch as one reproducible cause of multiplayer file errors; replies remain community advice.

Community report42.20.4 ISReadABook.lua Files Not Matching

Recent player-language evidence for a post-hotfix Lua file mismatch; community workarounds are not treated as official fixes.

Platform docsSteamCMD Documentation

Platform documentation for installing and updating dedicated server applications through SteamCMD.