I've had this issue for more than a year now. Sometimes it works, most of the time it doesn't. I can't be the only one experiencing this? The status bar says "Running" but even after half an hour, nothing happens on the Watch. Installing to my iPhone works just fine but as soon as I target the Apple Watch, it gets stuck.
I've had this issue on and off since.... well, since there's been an Apple Watch ;-(
I find debugging an Apple Watch app very frustrasting as I can have a debug setup working as expected, then for an unknown reason, XCODE will take much longer than usual to compile and install the Apple Watch or sometimes cycle through "preparing device" & "installing [app name] watch..." for up to 20 mins (seriously, I use a timer). It will occasionally progress as expected or finally give up with an unhelpful "Unable to install [app name]" dialog.
First, if there are developers who have had dependable debugging experiences with XCODE + Apple Watch, would you please chime with words of encouragement?
Or if anyone has ideas of what to do other than restart XCODE, restart Apple Watch, restart iPhone in some magical order, please share your secret! ;-)
Or you wait for ages with this message then suddenly it springs to life before ultimately showing a dialog saying "Unable to Install ... WatchKit App".
Oh for a cable to the watch, or at least the option to prefer WiFi over Bluetooth when both available, but that's another story.
Normally I would have XCode saying: "Running .. on .. Apple Watch", then it would sometimes say " Unable to install ..".
However, after I removed "Connect via Network" in Window -> Devices and Simulators -> Paired Device the error stopped.
On occasion the app gets installed on the watch, but never launches, and the debug session never starts.
I'm wondering if it's maybe a faulty watch connection? For some reason I've also been unable to take screenshots on the watch, even if the option is enabled in the watch app. Pressing crown and button simultaniously will even make both watch and iPhone vibrate but there is no screenshot to be found in the camera roll of the iPhone. Does anybody else here experience this?