I've downloaded the Twain driver for Photoshop CS6 from Adobe and copied the Twain.plugin file to the Photoshop Plugin directory in Applications. I'm using a Mac with 10.6.8. I then restarted CS6 but there isn't a mention of 'Twain' in the Import menu? So also not my scanner. Which is an Epson Stylus SX130. Why not?
Is your scanner driver 64-bit?