Invalid file id
The request’s file id failed basic validation (empty, shorter than the minimum, or longer than 64 characters) before a normal “file not found” lookup.
Why this happens
Malformed grant body, truncated id in a client, or bad URL param on Member API download. Grant mint may map broader body-schema failures to this code. Distinct from File not found (valid-shaped id, missing row).
Diagnose and fix
1. Copy the full file id from My Files / the download URL — do not truncate.
2. API: send fileId as a string in the expected JSON/form shape.
3. Confirm you are not sending a folder id or empty field.
4. If the id looks valid but the file is gone, expect File not found instead.