When you feel the atx engage, if you give a LITTLE gas does it want to move, do you feel the car lurch? Are you sure your emergency brake is fully release ( I know dump question but you never know) If everything looks ok, the only other item I can think of that would keep your car from rolling when it is in neutral is the parking pawl shift lever in the trans has fallen off. You can switch gears but the pawl is locked - this is a far stretch....Did they remove your trans to rebuild it? If so then they may have not tightened this down.
Again, these are some suggestions to check.......
Regards,
Bob
