Twitter API Postman: Code 32: Could not authenticate you

For anyone still having issues...

My problem was that the Content-Type: application/x-www-form-urlencoded header was not set for my POST request when testing with Postman. Once I added that, all was well.

Under the "Authorization" tab in Postman, choose "Request Headers" from the "Add authorization data to:" drop down.

Useful reference: https://developer.twitter.com/en/docs/basics/authentication/guides/authorizing-a-request.html

Another thing to check is the ! character in the status that's being posted. Ensure it's encoded correctly.

See here for more details: https://groups.google.com/d/msg/google-appengine/6ILDt39anbs/gEwMVBNJLkYJ

Error 32 "Could not authenticate you" can also happen when the content of the tweet triggers the Twitter censorship filter.