multiple images upload doesn’t work

Hi,
thanks for this plugin, it’s really great!

I am trying to allow users to submit more than one image, and I can’t make it work.

In the image settings, I have enabled Maximum number of images to 20, but, it doesn’t allow me to select more than one, when I use the browse button, and, after I select an image, the text to add more images appears, but it is only text, it is not a clickable link to upload other images.
Any idea why?

thanks a lot