Hi, Some synths don't play when their windows are active, eg: while changing patches or changing parameters inside the plugin's window. I have to activate Ableton's window to be able to hear sounds. I use the laptop's keyboard for playing. I have just noticed that when I am in the plugin's window my keyboard doesn't send midi signal to the synth. It happened to me when I started playing with Vast Dynamics Vaporizer2 recently but I had this issue with few other synths before.

 

Hasn’t anybody got such ailment with not playing active synth window in Live?