GCP doesn't consider it to be an "outage" if you are able to access a website (e.g "youtube.com") and get a 200 OK response. So, when you go to the status page for the cloud service, it will show green checkmarks, meaning everything is ok.
But, the video you are trying to watch won't load, and will throw a 500 error. But this isn't considered downtime, for them.
Yeah I've had nothing but grief with those outage detectors. They seem to be really optimistic and not take into account the web of CDN's that contribute to the 'uptime' of a website