FBSOpenApplicationErrorDomain error 3 when trying to launch a watch kit app on a physical device
This was a permissions issue on the Apple Watch.
To fix:
Launch the app once manually (not through Xcode).
You will see the following message:
Untrusted App Developer
Do you trust the developer "..." to run apps on your Apple Watch?
[Trust]
[Don't Trust]Tap Trust.
- Now you can run the app through Xcode with no issues.
Had same issue:
- Go to settings on iphone
- General > Device management
- choose your developer app from list
- click on trust