Error 400 on /kraken/users?login=xxx

You need to set the API version to v5. The default v3 does not have this “/users?login=” endpoint.

See the documentation for the preferred method(s): https://dev.twitch.tv/docs/v5/guides/using-the-twitch-api/#api-versions-and-mime-types

Accept: application/vnd.twitchtv.v5+json

Non-header methods include: