Works ok for me:
{
"channels": 24585,
"viewers": 743808
}
Make sure your request includes the v5 accept header
curl -H 'Accept: application/vnd.twitchtv.v5+json' \
-H 'Client-ID: uo6dggojyb8d6soh92zknwmi5ej1q2' \
-X GET 'https://api.twitch.tv/kraken/streams/'