You don’t send a 202 you send a 200, with the bodt as the hub_challenge GET argument (which I’ve been receiving as hub_challenge rather than hub.challenge. So cross check what you are receiving
The response to the (cURL) subscribe request is a 202 Created.
You must only send 200’s to Twitch.
So:
if(request.query['hub.challenge'] != null){
response.send(request.query['hub.challenge']);
}