Did you check to make sure your hardware meets the requirements for 3D?
Note that this is boilerplate text.
If you give complete and detailed information about your setup and the issue at hand,
such as your platform (Mac or Win),
exact versions of your OS, of Photoshop (not just "CS6", but something like CS6v.13.0.6) and of Bridge,
your settings in Photoshop > Preference > Performance
the type of file you were working on,
machine specs, such as total installed RAM, scratch file HDs, total available HD space, video card specs, including total VRAM installed,
what troubleshooting steps you have taken so far,
what error message(s) you receive,
if having issues opening raw files also the exact camera make and model that generated them,
if you're having printing issues, indicate the exact make and model of your printer, paper size, image dimensions in pixels (so many pixels wide by so many pixels high). if going through a RIP, specify that too.
someone may be able to help you (not necessarily this poster).
a screen shot of your settings or of the image could be very helpful too.
Please read this FAQ for advice on how to ask your questions correctly for quicker and better answers:
Hello! Maybe it will be helpful for those who use Windows. My 3D didn't work, I went to Preferences=>3D=> Allowed VRAM (the line on the very top of the window with preferences). Mine was set up for 111Mbs, I went all the way up to 1010 Mbs and clicked "Save". I closed the Photoshop and Opened it again. It works now. Basically, allow more RAM for the 3D. Hope this helps. (P.s. I don't know if MAC would have the same options for problem resolution)