I am getting the same error using https://github.com/smurthas/fitbit-js
I did
git clone https://github.com/smurthas/fitbit-js.git
cd fitbit-js
npm install
cd example
node test.js [Consumer Key] [Consumer Secret]
I have the callback URL set to http://localhost:8553/ (also tried http://localhost:8553/getStuff)
I opened http://localhost:8553/ in a Chrome when I was logged-in in another tab. I sent to https://www.fitbit.com/oauth/authorize?oauth_token=... was given the Deny/Accept option. I clicked Accept, was sent to http://localhost:8553/?oauth_token=...&oauth_verifier=... which then sent a 302 redirect back to https://www.fitbit.com/oauth/authorize?oauth_token=...
I tried this in Safari and Firefox - I have never logged into Fitbit in these accounts. I also tried clearing the cache and got the same result. Same when using incognito mode.
Moderator edit: edited title for clarity
