I have enabled the three-finger lookup, but it is not working since I upgrade to Yosemite. How to fix it?
Are you running Scroll Reverser? It causes the bug. Just quit Scroll Reverser.
I had a similar issue and used these two commands to disable and then re-enable bluetooth. Seemed to revive my issues.
However I have noticed that 3-finger lookup works in some applications and not in others. For instance no problem in my web browsers but not so great in my vm or a few Microsoft products.