Diagnose DayZ startup, mod and joining failures without wiping persistence

A DayZ service can be running while a particular client cannot enter it. First distinguish a server process that exits, a connection that never reaches the game, and a player rejected during login. Each needs different evidence; deleting the world's storage can destroy progress without fixing any of them.

1. Preserve the complete error

Copy the full client error code, message and any named file. Save the UTC time of one attempted connection.
Record whether every player is affected or only one person, and whether the problem followed an update or mod change.
Check fresh server output from that same attempt. Keep a private copy before another restart overwrites useful context.

Bohemia's error reference separates connection problems, server rejections and kicks. A code alone is less useful than the code plus its additional text. Avoid repeatedly retrying while the server is deliberately shutting down or updating.

2. If the process does not remain running

Start with the first substantive startup error, not the final message saying the process stopped. Check the configuration path selected by -config and the profile directory selected by -profiles. The profile directory is also where server logs are normally written; a template can choose its own location.

Look for a missing file, malformed configuration, failed mission load or a mod path that does not match the files present. Preserve the last known working startup settings for comparison. Do not clear all logs, replace the whole server folder, or treat a crash loop as proof of a damaged save.

3. If it runs but cannot be reached

Recheck the assigned game endpoint and any separately allocated query endpoint. A successful browser listing only proves that the query path returned information. Conversely, an absent listing does not prove that direct player traffic is impossible. Give support the exact address and port you tested rather than opening a broad port range yourself.

Compare client and server release branches and builds before troubleshooting mods. If another player can enter using the same endpoint, compare the failing client's build, enabled content and full rejection text instead of immediately changing the server.

4. If the error names a mod or signature

Match the named PBO and Workshop item to the intended server mod set. Bohemia documents mod loading through -mod and public signing keys in a mod's Keys folder. Review the affected mod's installation instructions and dependencies on a test copy before changing production.

Do not disable signature verification, BattlEye or authentication to make the error disappear. Do not delete every mod and reinstall the collection over a live world. Some content changes affect stored items or scripted systems, so keep the matching world and mod-data checkpoint before a controlled correction.

Verify one correction at a time

Repeat the same player's connection and check that the expected character and world remain intact. Escalate with the first startup error or full rejection, UTC time, server build and recent changes. Share raw logs privately because they can contain player identifiers and server paths.