A lengthy Google help forum filled up with complaints from owners, who said they could no longer say, “OK Google” and speak a search item or voice command from any screen. Instead, they were forced to launch voice search through the app or search bar.
A Google community manager says some “compatability work” by Google’s engineers accidently broke the feature, but it’s now restored. She indicated you should be running the latest version of the Google search app to get the feature up and running again.
The impact on you: If you have a Galaxy S6 or S6 Edge the hotword detection should start working again soon. If you want it faster, or if it doesn’t come back at all, Android Police suggests disabling Google Play Services, which reverts it to the app’s factory version. Then re-enable and update Google Play Services. Next, go into the Google app’s settings for Voice > OK Google detection. The “from any screen” option should return.