I apologize for the late response, thank you for being patient! Were you able to fix that G screen issue? If not, I'd be happy to help you out. If you've already attempted to do a factory reset, but you're still stuck on that screen, I'd encourage you to speak with Chromecast Support. To have them reach out to you, go ahead and fill out this form, then let me know when you have done so.
I look forward to your response, and if you have any other questions or concerns for me, please let me know.