Pairing problems between smartwatches and smartphones tend to happen from time to time, as has been the case with the Nexus 5X and the Samsung Gear S2, and Bluetooth pairing problems are part of the consequence of having to pair these two devices to begin with.
Have you picked up the new iPhone 7 and noticed that your Moto 360 2nd-generation or ASUS ZenWatch 2 (or practically any Android Wear smartwatch) isn't pairing with it? Chances are, the Android Wear smartwatch on your wrist is the problem -- and Google has confirmed it.
iPhone 7 and iPhone 7 Plus users have been making the situation known to Google, with one in particular saying that his TAG Heuer Connected Carrera (that's the current and very first TAG Heuer smartwatch) isn't pairing with his new iPhone 7:
I've got a TAG Heuer Connected that was working fine with my iPhone 6 even after I upgraded to iOS 10, but then since I unpaired to connect to my new iPhone 7 I haven't been able to pass the pairing screen. I've tried with both phones, even tried to after downgrading the iPhone 6 to 9.3. I've also tried a factory reset through the 'Android dead robot' as advised by TAG, but didn't help, none of the phones get the code from the watch. Thanks!
Another said his Moto 360 2nd-gen. has had the same streak of bad luck, with the Android Wear app doesn't register the pairing and doesn't bring up the "accept message" popup that indicates everything is working normally.
After 9to5google decided to write the search engine giant about the issue, Google wrote to confirm that the ASUS ZenWatch 2, Moto 360 2nd Gen., Moto 360 Sport, TAG Heuer Connected Carrera, and the Fossil Q Founder are all affected smartwatches that won't pair with the iPhone 7 or iPhone 7 Plus.
Android Wear has iOS compatibility now, allowing iPhone users to still use their smartwatch of choice and get iPhone notifications, but the iOS experience is limited when wearing an Android Wear smartwatch (Apple likes to lock users into WatchOS with the new Apple Watch 2 instead). Google has alerted Apple for now and is working hard to fix the issue, but if you're thinking about getting the iPhone 7 or 7 Plus, you might want to refrain until the Android Wear smartwatch pairing issue is resolved.
That is, unless you want to render your Android Wear watch a wrist paperweight.