Any idea why elements is generating error in log:

receiver: failed to bind?

Just had the same problem after updating to Catalina, with no corporate security on my device. Like @trbielec I could see karabiner_observer in my System Accessibility Settings but there was no karabiner_grabber. I fixed this by clicking the + button, searching for karabiner_grabber, and adding it that way. After making that change, Karabiner-Elements works again!