I work for a distributor of Sena and we can't seem to get any of them to work with VOX call. All of the other voice command features work, we just can't answer calls using voice.
I've been through the list of things to try;
factory reset, update, enable & disable VOX, check the app, check the device manager, check different mics, different units, the whole lot.
None of them answer calls with VOX.