I know this is an old thread, but I stumbled on it while wasting hours today trying to get a simple 'watch only' Xcode app installed on an Apple Watch. Here's what finally worked for me. After all of the other items mentioned (restarts; setting the developer mode to yes on both the iPhone and Watch; switching between network & direct connection; adding & removing the iPhone from 'Manage Run Destinations'; and probably some steps I'm forgetting). I did have to clear one last hurdle which was signing the app, but I did that as a 'personal' team and restarted Xcode to get around that issue. But even with all that, I kept having problems getting my app to load on the phone. So I tried one last trick that worked for me when everything else failed. I put the watch on! That kept it unlocked and the code was able to deploy successfully to the watch through the phone (I used a direct connection instead of the network). It still took some time, saw various messages in Xcode about loading symbols from the phone or installing the app, but it finally worked! From a developer experience, it was a truly miserable one today. This should have taken me 5-10 minutes, tops; instead, it took me 2-3 hours, maybe more.