Thanks for reaching out and I'm sorry for the trouble this may have caused you.
A few questions:
Make sure your devices are within 15-20 feet of your router. Also, try resetting your device to its default settings.
I have Google home mini and Lenovo Google Home Display. My system has been working for years. I got a message that all my devices managed by the Geeni app have been removed. The devices are still working from the Geeni app so they haven’t been unpairs they just won’t appear in the Google Home app. I have tried relinking Geeni and it links successfully but then it does not give me any device to add to Google Home. I am using a private network.