It looks like you set up your headers wrong. Twitch does not recognize the Authorization header, instead you put the OAuth token (without the oauth: prefix) under Client-ID. Hope my suggestion helps.
I still got the same error, and I have refreshed the caches of the site. Plus when I look at the Docs locatated here https://dev.twitch.tv/docs/v5/reference/channels/ it tells me that I need the Authorization, Client-ID, and the Accept Headers
I just looked at the docs and you’re right: it needs an extra OAuth token for the Authorization header. I’ve tested it myself using the same exact Client ID and got a 404 error. I don’t know how this works exactly, but there’s an alternative method:
Get the username’s ID with this URL: https://api.twitch.tv/kraken/users?login=username
Use that same user ID to get its info, for example, https://api.twitch.tv/kraken/users/1234567
It should give you the exact output without the account’s email address, obviously for security reasons. Apologies if it isn’t related, but I find it easier that way.
You can easily get an OAuth token at http://twitchapps.com/tmi. Don’t worry about the name, just about any valid OAuth token linked to an account should work.
I removed dataType: jsonp since Kraken supports CORS so there isn’t much of a need for jsonp. Also, I don’t think that works with headers, added the Accept header to specific the latest API version, and also changed the url to remove the “s” in channels. I think there is an error in the v5 docs since this request was singular in previous API versions.