I'm having the same issue, it's been a few months now, says "sorry, it looks like that device isn't set up yet".. even though it was and seems to still be set up... I'd love to get this sorted out as well.
I’m sorry for the trouble this has caused you, let me help you out.
A few questions: what Google Home or Google Nest speakers and displays do you have? When did it start happening? Also, do you have other smart devices?
Give these steps a try:
Hope the steps help!