No sound is playing at all from Arché's plug-in.
Arché differs from most virtual instruments in the sense that in order to produce a sound, you will not only have to play a note on your keyboard, but you will also have to strike the virtual bow of Arché at the same time.
When using Arché with Touché and its companion app Lié, you will find a set of presets in Lié's browser that are installed with Arché. Those presets have the virtual bow readily mapped to your Touché. You just have to apply pressure to the upper side of the touch-plate of Touché while holding a note to produce a sound.
When using Arché outside of this scenario though, you will always have to manually map the virtual bow to a MIDI controller element to get a sound out of Arché. Since the sound is produced with back-and-forth movements of the respective controller, a mod wheel or touch-strip/ribbon is recommended for the smoothest action.