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.
This is so ridiculous and annoying. I don't even develop apps for the watch, yet Xcode constantly wants to prepare the watch for development and can't get it done. Seriously, Apple? Why don't any of you care about this problem?
The only solution for me is to switch off the watch while working on apps.
4 years passed...