I have the same issue. Over the last week or so I was getting a “there is a glitch” message when I used voice commands. Rebooting the speaker did not help, so yesterday I did a factory reset and am now getting the message that “your device isn't set up yet, to get started download the google home app.” I spoke with a B & O customer support person and he said  it’s a Google problem and they are working with Google on a fix. Of course, I have no way of knowing if this is true.

It is true this is a Google problem. There are many threads (non B&O) about this. You can try to create a completely new Google Account and try that way. I have a BS1 with GVA but don’t use the GVA and of course it is working on my device (sadly a wasted feature for me) 🤷🏻‍♂️

I have the exact same problem its so annoying that it's suddenly stopped working.  I'd be interested if you hear about a fix.

Unfortunately exacty the same thing in South Africa:

Google Assistant says you have to setup, even though according to Google Home App, it is connected. 

I am able to cast to it via Spotify, but is is very buffery!

Missing the ability to play radio via Tune-In. Very frustrating in these time of Lockdown.