Subject: OAuth 1.0 Invalid Signature - Code 8 - Need Help Debugging

[Dame Abe]

Hi FatSecret Support,

I'm getting a persistent "Invalid signature" error (code 8) on all OAuth 1.0 API calls, and I've exhausted all troubleshooting options on my end.

What I've tried:
- Reset my Consumer Secret and re-entered credentials
- Verified Consumer Key and Consumer Secret character-by-character
- Used the oauth-1.0a npm package (battle-tested library) for signing
- Verified my signature base string format matches your documentation exactly
- Tested with both hand-rolled HMAC-SHA1 signing and the npm library
- Confirmed my signing key format is: percentEncode(consumer_secret)&

My setup:
- Platform: Vercel serverless functions (Node.js 18+)
- Account type: Premier Free
- HTTP method: GET to https://platform.fatsecret.com/rest/server.api
- Method being called: food.find_id_for_barcode

The API was working previously with the same signing logic. Nothing changed in the code, but I'm now getting invalid signature on every request.

Could you check if there's an issue with my account or credentials? Please reply to the email address that sent this communication.

Thank you,
Damon Abramson

[seba...@fatsecret.com]

Hi Damon, thanks for reaching out, please get in touch with our API support team and provide them with your account email or API key then they can investigate further 
https://platform.fatsecret.com/contact