This problem is killing me! I have a Nexus 7, 10 and a M8. OK Google anywhere is working on the 10, used to work on the 7 then inexplicably stopped and has never worked on the M8. I've tried everything, reflashed the ROM(s) cleared Google search, uninstalled it. Same with play services. It's really frustrating!
Everything's up to date. Once the trainer appeared when I enabled audio history but then the app crashed and it's never happened again. Totally stumped!