Hi Mary,
The main issue I see with this portrait is that it misses the very pronounced value changes in the large masses of his head and thus looks much flatter than the reference photo.
You might want to check out this thread:
http://forum.portraitartist.com/show...&threadid=1863
Your painting misses the large shadow area between his eyes, the shadow below his nose, the lower value of all of his face that is below the mouth. Also the dark shadow to the left of the eye on our left should not be nearly so dark.
Squint at your reference and look for the large shadow and light masses of the form and you'll see what I mean. If you have an image editing program like Photoshop, changing the reference and your photo of the painting to black and white may help you to see what I mean more clearly also.