The Watch paired with my iPhone is shown as the run destination, so I think it's connected. However the WatchKit app can't be installed on the watch.
watchOS 5.1.3 (S4) iOS 12.1.3 (iPhone 7)
Here's the screenshot of the alert:

I've tried many options but none of them work. 1. repair the watch, 2. clean the build, 3. delete the Derirveddata directory
The app is a newly created project which has no custom code.
What could be the possible season that the app can't be install onto the watch as it should?
Thank you in advance.