In case anyone else has this same problem---in the end, it turned out that somehow the files I was using were converted to CMYK. Once I changed them back to RGB, the 3D tools were once again available.
↧
In case anyone else has this same problem---in the end, it turned out that somehow the files I was using were converted to CMYK. Once I changed them back to RGB, the 3D tools were once again available.