The + sign is a url encoded space. As per https://github.com/justintv/Twitch-API/blob/master/authentication.md#scopes you must send your scopes with spaces separating them.
The + sign is a url encoded space. As per https://github.com/justintv/Twitch-API/blob/master/authentication.md#scopes you must send your scopes with spaces separating them.