If the light doesn't turn on at all (and, make sure you are really looking at the light, I just spent 10 minutes looking at the BUTTON waiting for one of my devices to power up), then it is not getting power or not booting up at all.
First, try a different power block and cable. If you still don't get any light at all then something has probably failed in the Chromecast device. Also, try plugging it in while it is NOT connected to a TV to see if the lights come on. There have been a few instances where the TV's port is actually causing a problem.
Unfortunately, if it's a Gen 2 device (round with a flexible HDMI cable) it is probably out of warranty since Google last sold those in 2018 and there is nothing you can do to get it repaired.
