not_found

HTTP 404. No such object for this app and mode.

What it means

The ID does not name an object this key can see.

Why it happens

The ID was made with a key of the other mode: test and live data are separate.
A typo or the wrong prefix (conv_ where msg_ is expected).
A message older than the retention period, or an expired file.
The path itself does not exist (for example a trailing slash).

How to fix it

Take IDs from the API’s own answers with the same key: GET /v1/conversations, GET /v1/events, the event your webhook received. If the object was made in the other mode, use that mode’s key.

curl "https://api.flow.engineer/v1/conversations?limit=5" -H "Authorization: Bearer $FLOW_MESSAGING_KEY"

Every error also carries hint, one sentence specific to your request, and doc_url, this page. Coding agents connected to Flow’s MCP server (https://api.flow.engineer/mcp) can call explain_error with the type to read this page.