Lighting Effects is dependent on your GPU and display driver.
You might have gotten a driver update through Windows Update that changed the behavior of your system. But you haven't described your computer, so that's speculation - you may not even have Windows. If you DO have Windows, you may be able to get an even newer/better display driver directly from the web site of the maker of your video card.
It's also possible that if you go into your Preferences - Performance dialog, press the [Advanced Settings...] button, and change to one of the other drawing modes you might be able to recover the functionality. Make SURE to close and restart Photoshop after making changes there.
OOPS! Somehow I missed that you said you're "Using Mac...". Sorry
Try the changes to the [Advanced Settings...] I described.
Also try a reboot, and possibly a preferences reset.