Be sure that you press AND RELEASE the Google button on the remote BEFORE speaking (i.e. don’t hold the Google button down while you are speaking to it). You only need to press it once and release, and then begin speaking. Also, to use Google Assistant, your remote must be paired correctly with your Stream TV Box. If your voice is not being recognized, you may need to re-pair the remote.
When I use Google Assistant for Voice Search on my Stream TV Box, it doesn’t seem to hear me.