Leo says that's by design. What he needs to do is put the phone into "disk mode," or "MTP mode" so that the computer will see it as a disk to mount. This should be in the settings. If it doesn't mount, try a different cable. If that doesn't do it, then there's something wrong and it could be hardware or software at this point. A driver may not be loading that the phone needs to broadcast that it's there. Resetting the phone will reload that. If that doesn't work, then take the phone back.