1. On your Android phone or tablet, touch and hold the Home button or say "OK Google" or "Hey Google."
2. In the bottom right, tap .
3. In the top right, tap your Profile picture or initial Settings. ...
4. Under "Assistant devices," select your phone or tablet.
5. Turn Google Assistant on or off.

I have an iPhone

I have a similar issue.  For example, in my den, I can’t say “Hey Google, add soap to my shopping list.”  To get you that information, you need to give me permission.”  But I can say, “Hey Google, play music in the den,” and “Hey Google, set a timer...”

So, it seems that it’s application/service dependent, and I have no idea how to change it.  Tried for 10 minutes on multiple occasions.

I’ve managed to fix it. I had to unlink the google assistant, re link about three times, the it started working. I can’t work out why this ended up working, but it did. 

It all seems rather clunky. Google assistant recognising whether there are any devices seems to be touch and go at times too. I can't get it do that with trying to get voice recognition - no devices found. Again, weird. 

IT, there’s always issues. : )

Hi, I had the same issue this morning and came across this post. And I just fixed it. Hope that helps! ( I use iphone and sonos beam)

1. In Google Assistant App, tap your profile pic/initials at the top right
2. then tap ”devices”
3. find your sonos device and tap
4. in the next menu, enable ”Personal Results”