Cannot connect to the debugger

“Cannot connect to the debugger. Since we could not locate the target IDE to start a debug session, this application will now exit.”
I get this message when trying to run my iOS application in the Simulator.
Xojo 2015 Realese 3.1
Simulator 9.1
Xcode 7.1.1
Any clues?

Are you launching the app from Xojo or from the simulator itself? The app must be launched for debugging from within Xojo. If you get that message when you press run then something is broken.

I am launching from Xojo

The project I was launching was made a year ago with a previous version of Xojo. I re-made it with the new version and everything works fine.