Uploading photos to PC- not connecting.

I do not use Icloud to back up my photos, because i take way TOO many. My storage is full, so I need to transfer the photos to my computer. I connected my iPhone to my PC to go to import the photos, however it says The Folder is Empty. I can still view the photos on my iPhone. Why wont the pictures show up on my PC? Could it be because my disc space is low?