The yellow (!) mark indicates that the device is in recovery mode. The error is likely caused by rebooting Chromecast multiple times without allowing it to go through its full reboot cycle. Try these steps:
- Unplug Chromecast from the power source. Leave it unplugged for 2 minutes, before plugging it back in.
- Make sure to plug the Chromecast directly into a wall outlet, not a TV USB port.
