Why won't my Nexus 7 transfer my pictures from my device to my computer ?

[AC Question]

My Nexus 7 shows up on my computer but it shows that there are no files in the file folder. It shows all of the pictures that I have already transferred to my computer on my computer and it shows all of them on my Nexus 7 accept the new ones I want to transfer from Nexus 7 to my computer it is not identifying the file folder. Can you help with this ?