As per
You need to send USERID not USERNAME, as you are declaring Twitch API v5
So for me I would send 15185913 not barrycarlyon
As per the example:
curl -H 'Accept: application/vnd.twitchtv.v5+json' \
-H 'Client-ID: uo6dggojyb8d6soh92zknwmi5ej1q2' \
-H 'Authorization: OAuth cfabdegwdoklmawdzdo98xt2fo512y' \
-X GET 'https://api.twitch.tv/kraken/channels/129454141/subscriptions'