This did the trick for me as well! Note that I'm not using Unity, nor do I have an associated Watch app. It seems Xcode simply wasn't regenerating the (automatic) provisioning profile when I added the capability, and deleting everything under "~/Library/MobileDevice/Provisioning Profiles" forced it. Thanks!

Nice find, liubonexo. I had the same issue (and failed attempts at recreating the icon set), but your workaround of using Xcode 13 to generate the folder, and then copying it over, worked for me. Thanks!