Over the last few weeks my Google Assistant devices (except for Google Assistant directly on the TV) has stopped being able to turn off and on my shield TV box. The response I get is a positive one "you got it. Turning off the master bedroom TV", but nothing actually happens. I have 2 other shield TV boxes in my house and it works with the other 2. Any ideas?
Update 1 ... To clarify, the problem is not with the connection and communication between the Shield TV and the TV itself. The problem is that Google Assistant cannot turn the shield device on or off, even if the shield TV isn't connected to a TV at all.
Update 2 ... Problem identified. With Google app 3.9, it works fine. With the update to Google app 3.10 which started rolling out on 8 May, the ability to turn the TV on and off through Google Assistant is broken
Update 3 ... Recent Google app update on Android TV fixed it
It stopped for me as well on my Shield TV. I was able to turn it on up until I think about May 20th. Since then, I've experienced the same issues as you.