Have a Galaxy S6 or Galaxy S6 Edge? Great! Want to use OK Google's hotword functionality from anywhere but the Google app or the Google Now launcher? Not great!
You see, for the past month or so since the S6 launched, there's been a slight issue with OK Google Everywhere on the Galaxy S6. Specifically, it just stops working completely. All the options except "From the Google app" disappear, voice model training goes away, and you can only use the 'OK, Google' hotword from the Google app or the Google Now Launcher (which is, essentially, the Google app).
Why? How? Who? WHERE? Nobody really seems to know... and that's a problem. The best we've got so far? A lone community manager response on the Google Product Forums.
Thanks for all of your feedback. We shared this with the engineering team when users initially reported it, and they've been actively working on providing a solution. We will provide another update soon.
Note: I'm going to be marking this post as 'best answer' only to surface my post to the top of this thread for new users' visibility. I acknowledge this is still an open issue, and we're looking into it - thanks!
That comment was left over three weeks ago, and no update has since been provided, nor has the issue been fixed for anybody. If you'll recall, the Nexus 9 had a similar problem for some users, but it was nowhere near as widespread or persistent - I don't think anybody's found a way to even temporarily fix this problem on the Galaxy S6 (but if you know a way, share it!). Thousands of complaints about the issue have piled up on various corners of the internet, so this issue seems near-universal in terms of affected users.
We've reached out to Google and Samsung for comment. Neither responded by the time this article was published.