The selection for 2-Sided Printing (Windows) or Two-Sided Printing Settings (OS X) is gray or not available. What should I do?

• Make sure you use a paper type and size that supports this feature. Automatic double-sided printing is only available if you select plain paper and these paper sizes in the printer software:
  • Letter (8.5 x 11 inches [216 x 279 mm])
  • Legal (8.5 x 14 inches [216 x 357 mm])
  • A4 (8.3 x 11.7 inches [210 x 297 mm])

  Note: Automatic double-sided printing is not supported on glossy, thick, and certain matte papers.