Chromecast 2nd gen after factory reset says device previously set up by another user

[robdood]

I've had multiple Chromecasts for years.  Recently they have stopped working inasmuch as although they show an image on the TV, no casting apps can find them (though the apps can find the smart TV etc just fine)

So today I decided to factory reset both the chromecasts I have (both 2nd gen), delete everything from my google home app and start over, hoping that it would improve things.  

But.. unfortunately I just get this error now when trying to set them up.  I've factory reset both devices several times and it's just the same! 

Screenshot of error 

What's the point of a factory reset if it doesn't delete all the stuff?!  

Any pointers greatly appreciated.  Is there any other way I can force these things to reset?

[MplsCustomer]

@robdood 

I'm just another Google Nest customer, but when this error occurs with cameras or doorbells, it usually means the factory reset was not successful.

Perhaps the "How to factory reset your Chromecast" page will help:

https://support.google.com/chromecast/answer/6254654

Or you could try contacting Support:

1. Go to https://support.google.com/googlenest/gethelp.
2. Select a category/product family, and type in a brief description of the issue, then click "Next".
3. Select your device from the dropdown, click "Other", then click "Next step".
4. Under "Resources", just click "Next step". (Clicking one of the listed links will bring up a Help page.)
5. Under "Contact options", choose to get a phone call or chat with the team, depending on availability in your country.