Troubleshooting

What to do when peers cannot reach each other, messages do not arrive, a call has no sound, or the app will not open or unlock, and where to look for diagnostics.

#Start here: Can people reach me?

Most problems between two people are reachability problems. Concord has a check for it:

• press Ctrl+K (Cmd+K on macOS) and choose Can people reach me?, or
• open an invite and click Can people reach me? beside the code.

The dialog states which situation this device is in and offers the one next step for it:

Below the verdict, The three ways in shows the state of each route: Same network, A port you forward and Somebody's rendezvous.

#Peers cannot see each other

Two peers can talk only if at least one of them can accept an incoming connection. Work through these in order:

1. Same Wi-Fi. Desktops on one home network find each other with no setup. This never works on Android, and many work and campus networks drop the packets, so do not rely on it there.
2. A rendezvous. If anyone in the group runs one, paste its address into Settings → Connection → Rendezvous server and click Save; it applies to new connections at once. Joining with an invite code from someone who uses a rendezvous sets it for you. Running your own is covered in Running a rendezvous.
3. A forwarded port. In Settings → Connection → Direct connection → Fixed port, enter a number from 1024 to 65535 and click Save. Forward that port, TCP and UDP, from your router to this computer, then restart Concord. Your public IP address is then inside every invite code you hand out.

If the check says you are reachable but has no fixed port, invite codes you already gave out go stale when Concord restarts, because the port changes each launch. Click Pin a port to fix that.

If Settings → Connection warns that the fixed port wasn't free when Concord started, another program, often a second copy of Concord, holds the port. Close it or pick another port, and restart.

#An invite code does not work

That code didn't open the door with Couldn't reach them — they're probably offline, or on a network this device can't get to from here means nobody at the addresses in the code answered. Someone who can admit you must be online when you join. Ask them to open Concord and try again, or ask for a fresh code. If it keeps failing, run the reachability check on both sides.

#Messages are not arriving

A message of yours shows Sending… or Not sent. It has not gone out. Click Retry once you are connected again, or Discard to drop it. Slow mode — you can send this in Ns means the channel limits how often you post.

A guild shows Catching up with N peers… This device missed an update to the guild's encryption and is fetching it from members who are online. It clears on its own.

A guild shows Waiting for someone with the missing updates to come online. Nobody online right now has what this device is missing. It clears when one of them connects. If you are the only member left, the banner says so and offers Continue from here.

Messages sent while you were offline never show up. With a rendezvous set, each message is also left, encrypted, in the rendezvous mailbox of every member device that was offline when it was sent, and collected when that device reconnects. The mailbox is a safety net, not storage:

• it holds messages for 14 days and up to 200 per device;
• it keeps them in memory, so a rendezvous restart empties it;
• without a rendezvous there is no mailbox, and missed messages arrive only when a member who has them is online at the same time as you.

Anything the mailbox dropped still arrives from any member who holds it once you are both online. To force a catch-up, open Can people reach me?; when the rendezvous is not answering, Try reconnecting re-dials it, collects the mailbox and syncs with connected peers.

A direct message from someone new never appeared. A DM from someone you share no guild with, have not verified and never messaged first goes to Settings → Privacy & safety → Message requests.

One person's messages are missing. Check Settings → Privacy & safety → Blocked users. The block list is kept on each device separately, so a phone and a desktop can disagree.

Notifications stop on Android after the app is closed. See Android stops receiving in the background.

#Calls with no audio or video

Microphone blocked — you're in listen-only mode. The operating system or browser refused microphone access. Allow it for Concord (or for the browser tab running the web build) and join again.

No microphone found or Your microphone couldn't be opened. No input device was found, or another program is holding it. Close the other program, or pick a different device under Settings → Voice & video.

You can join, but nobody hears anybody. If Hide my IP on calls is on in Settings → Privacy & safety, calls are forced through the rendezvous's media relay. A relay that is advertised but cannot carry traffic leaves calls connected and silent. Turn the setting off to test; if calls then work, tell whoever runs the rendezvous (see If it is not working). When the rendezvous has no media relay at all, the setting says so and calls connect directly.

#Linux desktop app

The Linux desktop window runs on WebKitGTK, which handles audio and video through GStreamer. Concord turns on the webview's camera and microphone support itself; the GStreamer plugins have to come from your system.

• This machine can't make calls: … the WebRTC plugins are missing. Install your distribution's gst-plugins-good and gst-plugins-bad packages (package names vary by distribution) and restart Concord. Everything except calls works without them.
• No microphone found while the microphone works in other programs usually means gst-plugins-good is missing.

The web build (concord-linux-amd64-<version>, which opens in your browser) uses the browser's own media stack and does not need these plugins.

The window is blank or the app crashes at start on Wayland. Concord picks a WebKitGTK rendering mode for Wayland on its own, and leaves it alone if you set one. To override it, start Concord with WEBKIT_DISABLE_DMABUF_RENDERER=1 in the environment.

#The app will not install or open

#Windows SmartScreen or Defender blocks it

Concord's Windows binaries are not code-signed, so SmartScreen warns about each new release.

• On Windows protected your PC, click More info, then Run anyway.
• If Defender quarantines the file, open Windows Security → Virus & threat protection → Protection history, find the Concord item, and choose Allow (and Restore if it was removed).

WINDOWS.md has the full steps, including a folder exclusion for repeated blocks. Every release asset is listed in SHA256SUMS with an Ed25519 signature, and the app checks that signature before installing an update.

#The web build exits at start

The web build serves its interface on 127.0.0.1:8787. If another program, or a second copy of Concord, holds that address, it retries for about five seconds and then exits with an error. Close the other copy, or start this one on a different address with CONCORD_WEB_ADDR=127.0.0.1:8788.

#Android stops receiving in the background

On Android, Concord receives only while its process runs. Settings → Notifications & sounds → Background → Stay connected (on by default) runs a foreground service with a persistent notification so the node stays connected while the app is closed.

• If messages only arrive when the app is open, check that Stay connected is on and that Concord is allowed to post notifications.
• Android 15 limits this kind of service to six hours in any 24. When the limit is reached, the notification disappears and the node keeps running only as long as Android allows. Opening Concord starts it again.
• Messages missed while the process was stopped wait in the rendezvous mailbox and arrive when Concord next runs.

#Forgotten passphrase

The passphrase is never stored anywhere and cannot be looked up or reset. On the unlock screen, click Forgot passphrase? and choose:

• Re-link from my other device — if this account is signed in on another device, link from it. Profile, guilds and history all come back. See Multiple devices and sync.
• Use my recovery phrase — enter the 24 words and a new passphrase. This restores your account key: you are the same person to anyone who has verified you. It does not restore data. The device starts with no guilds and no history; ask someone in each guild for a fresh invite, then restore a backup if you have one. See Backups and recovery.
• I have neither — start over (deletes everything) — wipes the identity on this device. Nothing can bring it back.

#Diagnostics and logs

Insights & diagnostics shows this device's state: database and attachment sizes, peers and connections, the rendezvous, bandwidth, whether the device is Reachable from outside, and for each guild whether it is in sync or healing…. Open it from Settings → Connection → Stats & diagnostics, with Ctrl+Shift+, (Cmd+Shift+, on macOS), or for one guild from its menu under Stats & diagnostics.

Concord writes no log file. Its log lines go to standard error, so to see them, start it from a terminal, for example on Linux:

./concord-desktop-linux-<version>

The headless concord binary and the rendezvous node log to standard error too.

#Where your data is

Everything Concord keeps on a device is in one directory, created readable by your user only:

It holds the encrypted identity (keystore.json) and the database (concord.db), among other files. Deleting it deletes this device's identity and history.

#CONCORD_HOME

Set CONCORD_HOME to use a different directory. Concord creates it if it does not exist.

CONCORD_HOME=~/concord-test ./concord-desktop-linux-<version>

Use it to keep data on another disk, or to run a second, separate identity on the same machine. Each directory is one device: never run two copies of Concord on the same one. Two copies at once also need different CONCORD_WEB_ADDR values for the web build.

Two more environment variables help when diagnosing connections, in the app and in the headless concord binary: