Did you copy over the .itl file as well as the media folder? You can copy over the .itl file and assorted support files if you left those behind you can copy them now. Or as I say in the user tip:
If you think that you've moved your library correctly but cannot see your expected content when you open the library, or you see cloud links to items which should be stored locally, then see Empty/corrupt iTunes library after upgrade/crash. If you have difficulty updating content see Repair security permissions for iTunes for Windows or Repair security permissions for iTunes for Mac as appropriate.
If you needed to import anything to the library then you didn't move it correctly and should revisit the process if you can.
tt2