Color is not vibrant or rich enough.
Quick Fixes for Lack of Color, Vibrancy, and Depth in Dye Sublimation
Ensure most ink is releasing from transfer paper.
Try increasing pressure, heat, and/or dwell time gradually on heat press/calender.
Note: Not all of the ink will transfer.
Ensure transfer paper is heavy enough in weight to hold the proper amount of ink.
Increase heat press/calender temperature and/or dwell time gradually to fully develop shades -- added pressure on heat press/ calender can also assist in increased transfer of ink from paper to fabric.
Note: Consistently changing temperature and/or dwell time can stress the heat press/calender. If possible, its best to only change one variable.