I can't transfer my pictures from camera to computer?

I have a Nikon P520 and HP computer and I can't transfer my pictures from camera to computer because my computer is saying "0 pictures are found" and I don't know why it's saying that. I took some pictures and videos about an hour before I tried transfering them. It's recently starting doing this and I don't know why! Could someone please help me out if anyone knows what to do that would be great thanks!

Tell us how you are attempting to transfer the photos.

My wife's computer (Lenovo laptop) won't do diddly with the SD card, but works fine with the camera directly connected to the computer with the cable that came with it. Shouldn't happen, but it does. Works just as well, if a little slower than directly from the card.

Once you do get the photos transferred with the cable, format the card in the camera. Usually the problem is the card, but not always.