A couple weeks back, we reported on a widespread problem with OK Google "From any screen" (AKA "OK Google Everywhere") on the Galaxy S6 and S6 Edge. Namely, it was gone. While the hotword still worked from the Google Now Launcher and other third party launchers with such functionality hacked in, most S6 and S6 Edge owners were unable to use the "from any screen" functionality because the option simply disappeared.
Now, it's reappearing! Yay! A large number of you have tipped us to let us know you're seeing the option back on your devices. I checked my Sprint Galaxy S6 this morning, though, and I still didn't see it - but I did manage to get it back anyway, and it only took a couple minutes.
If you're in the same boat, I'd recommend doing the following: if you're on a version of the Galaxy S6 where it is possible, uninstall updates to the Google app, update the application, and then go to the voice settings and "OK Google" detection. On some variants of the S6 on sale in America, though, this isn't possible - the app on the most recent firmware updates is the newest version, so there is no "factory" version to revert to. If that's the case for you, keep reading.
If the above method doesn't work or isn't available to you, you can try a full data clear on the Google app itself, which will sign you out of your device (warning: this might temporarily break some stuff), at which point you'll need to sign back in. Then you can check for the OK Google detection features in the search app.
If that doesn't do it, the last thing you can try is going to your application manager and disabling Google Play Services (which will revert it to the factory version of the app), re-enable it, then update Google Play Services back to the most recent version. You should get plenty of Play Services errors to direct you to Play Store page for the app, so doing this should be quick and easy. Then go into the Google app's settings for "voice," then "OK Google detection," and see if the from any screen option has returned.
I think the Google App "reset" should be enough (since most of these settings are controlled by that app), but if that doesn't work, you've got the slightly more nuclear options above.
Here's Google's response, indicating they are rolling out the fix to users now. It seems to be implied that there was a compatibility conflict with Samsung's S Voice app (surprise!). If you want 'OK Google' from any screen, that will mean S Voice hotwording is disabled except when the screen is turned off.
- Everybody who tipped us