I have somehow corrupted my development environment. "Run and Debug" builds my watch app succeeds, but fails to run in the simulator on any device with:

I get a similar error in Eclipse.
I have to start the simulator from a terminal since neither Eclipse no VS fail to launch the sim with "Unable to connect to simulator.", but this is a situation I have had intermittently for years, so I don't think it's the source of the problem.
I have failed to clear the problem reinstalling the SDK manager from scratch, first removing the cfg and ini files and going through the initial setup and downloading the device files.
I only have one version of the SDK loaded:

The devices appear to be correctly installed:

Any suggestions as to my next step? Running on Mac