> ## Documentation Index
> Fetch the complete documentation index at: https://developer.chatsyncs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# MCP troubleshooting

> Fixes for common problems connecting or using the ChatSyncs MCP server in Claude, ChatGPT, Claude Code, Codex, Cursor, VS Code and Gemini CLI: the connect page rejecting a key, Unknown application, Invalid redirect and This page expired errors, a redirect_uri or Missing issuer parameter error, a desktop app that never finishes signing in, ChatGPT asking to sign in again, missing tools, messages not delivering because of the 24-hour window, the wrong WhatsApp number, and subscriber or credit limits. Use when a customer reports the MCP not connecting or an action failing.

## Connection problems

<AccordionGroup>
  <Accordion title="The connect page says ChatSyncs did not accept that key">
    ChatSyncs itself rejected the key: it's mistyped, or it was regenerated after you copied
    it.

    Open the [**API Developer Console**](https://platform.chatsyncs.com/api/developer/console)
    and copy the key again, without a space at either end (the most common cause). If you
    regenerated the key recently, every older connection needs the new one.
  </Accordion>

  <Accordion title="A ChatSyncs page says “Unknown application”">
    In **Claude**, this means the connector was added with *Use Claude's published identity*,
    which ChatSyncs doesn't support. Remove the connector and add it again, choosing
    **Register automatically**. See [Claude](/mcp/apps/claude).

    In any app, it can also mean the app's registration is out of date: remove ChatSyncs from the
    app and add it again.
  </Accordion>

  <Accordion title="A ChatSyncs page says “Invalid redirect”">
    The app asked ChatSyncs to send you back to an address it didn't register, so ChatSyncs
    stopped, to protect your key. Remove ChatSyncs from the app and add it again. If it keeps
    happening, update the app.
  </Accordion>

  <Accordion title="A ChatSyncs page says “This page expired”">
    The connect page is valid for 10 minutes. Start the connection again from your app and
    paste your key within that time.
  </Accordion>

  <Accordion title="Cursor (or another app) shows an error mentioning redirect_uri">
    Until 5 October 2026 ChatSyncs refused sign-in addresses that start with an app's own name,
    such as Cursor's `cursor://`, so Cursor couldn't connect. That is fixed. Switch ChatSyncs off
    and on in the app (or restart it) and sign in again.

    If it still fails, the app is asking to be sent back to a plain `http://` address on another
    computer, which ChatSyncs refuses because it would expose the sign-in. Connect with your API
    key in a header instead. See [Cursor](/mcp/apps/cursor).
  </Accordion>

  <Accordion title="I approved the key, but the app still says it needs sign-in">
    Desktop apps such as Cursor get the result through your browser. The browser asks something
    like *"Open Cursor?"*: choose **Open**. If you missed it, click **Continue** on the ChatSyncs
    page, or start the sign-in again from the app.
  </Accordion>

  <Accordion title="Gemini CLI says “Missing issuer parameter in response”">
    ChatSyncs sends this detail since 5 October 2026: run `/mcp auth chatsyncs` again. If it
    still appears, connect with your API key in a header, as shown on the
    [Gemini CLI page](/mcp/apps/gemini-cli).
  </Accordion>

  <Accordion title="ChatGPT asks me to sign in to ChatSyncs again">
    Connections made before 5 October 2026 may not renew themselves in ChatGPT. Open ChatSyncs on
    [chatgpt.com/plugins](https://chatgpt.com/plugins), reconnect, and paste your key once more.
    New connections keep renewing.
  </Accordion>

  <Accordion title="The app says it failed to connect">
    Check the server address is exactly `https://mcp.chatsyncs.com/mcp`, with no typo and
    nothing added (not `/sse`). In apps that ask for a transport, choose **HTTP** or
    "Streamable HTTP": ChatSyncs doesn't support SSE. Then remove ChatSyncs and add it again.
  </Accordion>

  <Accordion title="It connected, but the assistant has no ChatSyncs tools">
    The connection is switched off for this chat. Turn it on:

    * **Claude:** **+ → Connectors →** switch on ChatSyncs.
    * **ChatGPT:** type **@ChatSyncs** in the message where you want it.
    * **VS Code:** **Configure Tools** in the chat box; make sure the server is started.
    * **Cursor:** **Customize →** check the chatsyncs toggle is on.
    * **Claude Code, Codex, Gemini CLI:** type `/mcp` to see whether it's connected.

    If that doesn't help, restart the app.
  </Accordion>

  <Accordion title="It looks connected, but every action says “ChatSyncs rejected the API key”">
    The key your app holds no longer works. Two usual causes:

    * **The key was regenerated.** Apps don't ask for the new key by themselves: reconnect
      each one. See [After you regenerate the key](/mcp/api-key#after-you-regenerate-the-key).
    * **You connected with the key in a header or in the address** (`/mcp/k/…`) and it's
      mistyped. These methods don't check the key when you connect, only on the first action.
      Put in the current key, or switch to browser sign-in, which checks it straight away.
  </Accordion>

  <Accordion title="I was asked for my key again">
    Your app's sign-in ran out, usually because the app went unused for over a year, or you
    removed and re-added ChatSyncs. Paste the current key and it reconnects.
  </Accordion>
</AccordionGroup>

## Messages not sending

<AccordionGroup>
  <Accordion title="The message was rejected and mentions a 24-hour window">
    WhatsApp only allows free-form messages within **24 hours** of the customer last messaging
    you. After that, only an approved template is delivered.

    Ask the assistant to send a template instead: *"Send them the re-engagement template."* If
    you don't have one, create it in ChatSyncs — see
    [Creating a WhatsApp message template](https://help.chatsyncs.com/docs/create-whatsapp-template).
  </Accordion>

  <Accordion title="Subscriber limit has been exceeded">
    Your plan's contact limit is full, and messaging a new number would create a new contact.
    Remove contacts you no longer need, or upgrade your plan.
  </Accordion>

  <Accordion title="The template was rejected with a format mismatch">
    The template needs something the assistant can't supply: an **image, video or document
    header**, a **carousel**, or variables that aren't **mapped** in ChatSyncs. Send that
    template from ChatSyncs itself. Plain text templates, with or without variables, work from
    the assistant; it asks you for any value it can't fill in.
  </Accordion>

  <Accordion title="It says the message sent, but nothing arrived">
    Ask *"check the delivery status of that message."* A message can be accepted by WhatsApp and
    still fail to deliver — a blocked number, an invalid number, or a phone that's been offline.
    Also confirm the number included the country code.
  </Accordion>
</AccordionGroup>

## Wrong number or wrong account

<AccordionGroup>
  <Accordion title="It sent from the wrong WhatsApp number">
    With several connected numbers, say which you mean: *"send it from the support number."* To
    see them all, ask *"show me my account."*
  </Accordion>

  <Accordion title="It says this account has no connected WhatsApp number">
    The API key is valid but no number is connected to that ChatSyncs account. Follow
    [Connect your number to ChatSyncs](https://help.chatsyncs.com/docs/connect-whatsapp-number).
  </Accordion>

  <Accordion title="It keeps asking which number to use">
    Your account has several and the assistant won't guess. Name the number once and it will use
    it for the rest of the conversation.
  </Accordion>
</AccordionGroup>

## Frequently asked

<AccordionGroup>
  <Accordion title="It refuses to message my whole contact list">
    There's no bulk-send ability, on purpose — see
    [the tool reference](/mcp/tools#frequently-asked). Use
    [Broadcasting](https://help.chatsyncs.com/docs/send-bulk-whatsapp-messages).
  </Accordion>

  <Accordion title="It asks me to confirm every single action">
    That's your AI app's own safety behaviour, not ChatSyncs'. Most apps let you approve a tool
    for the rest of a conversation, or set read-only abilities to run without asking. Keep
    approval on for anything that sends messages.
  </Accordion>
</AccordionGroup>

## Still stuck

Tell support:

1. What you asked the assistant to do
2. The **exact** error text it showed you
3. Which app you're using (for example claude.ai, ChatGPT, Cursor, Claude Code) and how you
   connected it (browser sign-in, header, or key in the address)

<Warning>
  **Never include your API key** in a support message, a screenshot or a bug report. If you think
  it's been exposed, regenerate it immediately on the [**API Developer Console**](https://platform.chatsyncs.com/api/developer/console).
</Warning>


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