Top 5 n8n setup problems (these match the setup page's messages)
Open setup-page/index.html and press Test it, or use Something stopped working? to rerun the free check.
- "Your n8n refused the upload key (HTTP 401/403)". The Header Auth credential must have Name
X-Upload-Keyand exactly the key you send. Pick the same credential on Receive files (webhook) and Send file to the extractor. - "Webhook does not exist (HTTP 404)" or "Could not reach…". Publish (activate) the workflow and use the Production URL ending in
/webhook/invoice-extract, not the Test URL. - "n8n hit an error (HTTP 500)". Open Executions and click the red node. Usually the OpenAI credential is missing or out of credit, the Google Sheets login is not picked, or a tab is not named exactly
Invoices/Line items. - The upload form says it cannot reach the extractor.
webhook_urlin Set form settings must be your Production webhook URL (the setup page fills it for you). - A sample comes back as
reviewwith "duplicate". You sent the same sample twice; that check works as designed. Delete the test rows and try another sample.
Still stuck? Use the support page: https://oarsmanai.com/support/
| Symptom | Fix |
|---|---|
| claude.ai does not show Upload a skill | Turn on code execution (Settings > Capabilities). Skills need it. |
A file is listed as password-pdf |
Open it with its password and save an unlocked copy (Print > Save as PDF), then run again. The skill will not guess its contents. |
| Many documents go to review | Read the reasons in review.md. "total_mismatch" with a small difference usually means a tax or shipping line was missed; ask Claude to re-read that document. |
| A date is flagged ambiguous | Nothing on the document proves day-first or month-first. Tell Claude which order your suppliers use (validate.py --dayfirst yes/no). |
| A bill you already entered was not caught as a duplicate | Attach last month's invoices.csv (or point n8n at your sheet) so there is a ledger to compare against. |
| n8n: OpenAI error or empty answer | Check the OpenAI credential and model name in the settings node. Failed reads go to review; nothing is saved as ok. |
| n8n: nothing appears in the sheet | The tab names must be exactly Invoices and Line items with the headers from n8n/sheet-template/. |
| n8n: Gmail trigger does nothing | It ships disabled on purpose. Enable it in the workflow after connecting Gmail. |
| Tests say pdfplumber is missing | pip install pdfplumber pypdf openpyxl (Claude's sandbox already has them). |
FAQ
Who reads the documents? An AI model: Claude in the skill, OpenAI (your key) in n8n. Scripts then check the arithmetic, dates and duplicates.
Is it accurate? On our synthetic samples the checks behave as tested. Accuracy of the AI reader on your real invoices is not measured; check the review list and spot-check new suppliers.
Does it post to my accounting software? No. It produces a spreadsheet (or sheet rows) you import yourself.
Does it work for GST and VAT invoices? Yes, CGST+SGST and multiple VAT rates are added up and checked. It is data entry, not tax advice.
Where do I get help? README.md, n8n/SETUP.md and this file. There is no call, chat or email support. Fixes ship as new versions at your download link.