Xcode 7.2 can't attach to iPhone with iOS 9.2

Question

For development purposes, I already put iOS 9.2 beta on my iPhone 5s. Of course, I also installed Xcode 7.2 beta.

When I want to run an app extension (keyboard) on the device, the app builds properly, gets installed on the iPhone and started. Then, however, I'm presented with this message in Xcode:

Could not launch "MyApp"

process launch failed: failed to get the task for process

Does anyone know how to fix this?

EDIT: With the final release version if Xcode 7.2, the message changed to

Could not launch "MyApp"

unable to attach

Answer 1

Now I feel stupid...

I was signing the app with a distribution certificate and provisioning profile. With iOS 9.1 it worked, however. Now, I simply created a development provisioning profile and it's working.