I also use the Lenovo X1 (though Yoga, but think it's the same audio card etc). It works in my end, but I might run with non-default audio settings.
And when you say it's not working; what is happening? Just trying to pair forever?
Could you please help verify a theory; Right-click volume in system tray, select Sounds, the "Recording" tab and open properties for the Internal Microphone (assume it's the Conexant SmartAudio HD). Could you take a screenshot of settings in the Advanced tab? And after that, try to disable the audio enhancements and restart Proximity?
We have done some changes in how we handle ultrasound recording in Proximity 3.0, might end up reverting that in 3.0.1.
I took screen shots on my X1 Carbon. Sound tab and error message showing on proximity when try to use. Appreciate your help