Google is still not confirming the cause of the Chromecast outage, but it was almost certainly the result of a certificate expiring after 10 years. It would seem there was no one keeping an eye on the Chromecast's ticking time bomb,

If your old Chromecast stopped working a few days back, you were far from alone, as unexpected failure seemed to hit second-generation Chromecast and Chromecast Audio devices en m