There are two types of DVD+VR and DVD-VR discs:
2. Open (to allow for further recordings)
Studio will only import finalized DVDs. The open type (not finalized) will appear as an empty disc and can not be imported by Studio. Make sure that the discs are finalized before attempting to import them into Studio.
These discs must be imported though the Import DVD Titles feature. Do not try to import the files on these discs from the file folder icon in the Edit mode.