Finally got it on my Voyage today. The only one that notified me with a popup was my Oasis2. The Oasis1 and the Voyage didn't and I had to look in the device settings. Oasis1 of course is in a cover so I don't see it there. Voyage is my take along device and is in cover also when I use it that way.
I use my Oasis2 only in the house though and its never in a cover so now I can see the cover. Its kind of neat as I have been looking at it and see what I am reading and instead of doing something else, I picked it up to read. Like it reminded me to get a move on.
I been in a really bad reading funk since last year and its taking me a long time to read a book, which is very unusual to me. So I been picking it up more often since I got the feature.
eta: adding that I did not restart any of the kindles, the feature just appeared. I did have wifi on the whole time on all 3.