A Fillo file answer has two parts: the browser transfers the bytes to the connected storage provider, then the submission references the verified file record. Find the stage that failed before retrying the whole form.
Check the field rules
Compare the selected file with the published upload field:
- File size at or below the field limit.
- A MIME type or extension that matches the accepted types.
- A file count within the field's maximum.
- A required upload has to finish before submission.
Changing a draft field rule doesn't change the published form until you publish again.
Confirm storage is ready
A form with file uploads needs an active supported storage destination before it can be published. Open Settings > Connections, repair Google Drive, Box, or S3 access, then confirm the form still points to that storage configuration.
For S3, the respondent's browser uploads directly to the bucket with multipart transfer, so the bucket has to allow the actual form origin, the required methods, and headers. A provider 403 commonly points to bucket CORS, expired signing data, or credentials that can no longer complete the multipart lifecycle.
For Google Drive or Box, confirm the connected account still has access to the target and hasn't revoked Fillo. If authorization is stale, reconnect the account before submitting again.
Don't reuse upload sessions
Each upload session is bound to its form, workspace, file metadata, and authorization. Don't cache a signed upload URL, file token, or multipart ID for another file or a later page load. If a transfer was abandoned, remove the failed item and select the file again to create a fresh session.
Inspect the network sequence
Use the browser network panel to find the first failure:
- Session creation at Fillo.
- One or more direct provider upload requests.
- Provider completion.
- Fillo verification and response submission.
Keep the status, response body, storage provider, file size, and request ID. Don't attach private bucket credentials or signed URLs to a support message.
Related
- File uploads: Configure field limits and connected storage.
- Blocked by CORS policy: Repair browser-direct S3 origin rules.
- Form failed to publish: Connect storage before making an upload form live.