Yosemite three-finger lookup not working
Solution 1:
Are you running Scroll Reverser? It causes the bug. Just quit Scroll Reverser.
Solution 2:
The problem is with force touch if you have one of the new macbook pro - if it's on force touch under trackpad -> point and click -> Lookup and data detectors then change it to tap three fingers and it should work.
Solution 3:
Have you tried looking into System Preferences > Trackpad? I can't tell if you are referring to Mission Control swipe up with three fingers, but that's definitely still under the menu in trackpad and can be enabled.
Solution 4:
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.