That suggests you did not send the v5 header
Here is the example
curl -H 'Accept: application/vnd.twitchtv.v5+json' \
-H 'Authorization: OAuth cfabdegwdoklmawdzdo98xt2fo512y' \
-H 'Client-ID: uo6dggojyb8d6soh92zknwmi5ej1q2' \
-X POST 'https://api.twitch.tv/kraken/videos?channel_id=44322889&title=Test video'
Note the Accept header of value application/vnd.twitchtv.v5+json
It’s required for Kraken in order to route from v3 to v5