How come when I try to "pin it" on Pinterest, my pins are not pinning?

I have tried a bunch of times, apparently unsuccessfully, to pin stuff on Pinterest. I have the “pin” downloaded, because when I look at my favorites bar, I see “pin it.” Yet when I click on “pin it” over a photo, it goes to the box where I see the number of people that have pinned that, and the “pin” box, I click on “pin” and the photo flashes once or twice, and nothing happens and the count does not go up. When I click on “my pins” I have none. I have tried single clicking and double clicking, and same results: photo flashes, count does not go up, pins do not take.

What could be the problem?