1. Do you see a brick wall in front of the blue world icon at the bottom of LW's interface? (sample image)

2. Send them a magnet link of one of the files you wish to share, then see if they can download it; How to use Magnet Links & Direct Connect

3. Go to LW's menu bar, Tools > Options > Uploads > Slots & make sure both boxes have at least a number of 1 or higher. (Sample image, which is an image I posted for someone who wanted to limit uploads to one per person. You may wish to have these set higher.)