Zhao Yitian

Dear Titifunk,
Sorry for replay late, just came back from NAMM show.
We tested with Logic Pro 10.3.0 and did not find any problem. So no idea about what was wrong.
Anyway, please try to make sure your Xkey Air was paired and the Blue LED keep lighting, then open the Logic again.

Mac OS:
Turn on Bluetooth.
Open Audio MIDI setup native application (Applications/Utilities/Audio MIDI Setup.app)
When MIDI studio is shown, double click on Bluetooth icon.
Click the Xkey Air you want to connect to.
The connected Xkey Air will appear as a MIDI device in all applications that respond to MIDI.