Yea, I've been googling this issue too. Ihave the Sprint S5. From what I've read it seems that the latest update to KitKat 4.4.2 has broke the wake up from sleep for Svoice. Every once in a while I AM able to say OKAY GOOGLE from the home screen . But even that's random. Either way I'm not sure if this is a Samsung issue or a Google issue...meaning... who the heck is going to fix this!
I just remembered there is a work around of sorts that I read. It was said that you can enable CAR MODE in settings and then s voice will work. However I am not sure if you give up anything by doing this ie phone calls, Internet. etc
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