Twitch stream on my website constantly gone

Nothing has changed recently.

Your code doesn’t seem to use an oAuth token, and you seem to be using client_id as a query string param, helix only accepts ClientID and token via header

This change came in quite a while ago, not last week

You’ll probably use an App Access token:

You may also be interested in EventSub as eventSub will tell you where a channel goes live/offline and saves a lookup