Webhook subscriptions failing

API
3

It is an express server indeed, the subscription create request looks like this

fetch('https://api.twitch.tv/helix/webhooks/hub', {
            method: 'POST',
            headers: {
                'Client-ID': config.twitchID,
                'Content-Type': 'application/json',
                'Authorization': `Bearer ${data.access_token}`
            },
            body: JSON.stringify({
                'hub.mode': 'subscribe',
                'hub.topic': `https://api.twitch.tv/helix/streams?user_id=${config.streamerID}`,
                'hub.callback': 'http:// "My callback url" :3000/twitchhook',
                'hub.lease_seconds': '864000'
            })
        })
        .then(res => res.json())
        .then(json => console.log(json));

the subscription create request seems fine to me as I do receive a GET request from twitch but at this point I’m convinced it could be anything