upload multiple images does not start

I want to upload images to a gallery that has already been created. The images are jpg files in high resolution with a total amount of 80 MB.

If I select them all and push the button for upload nothing happens.

Hopefully this can be solved.
Currently I post my images only to facebook because their gallery works as expected. ngg in contrast shows its age…

http://ww.wp.xz.cn/extend/plugins/nextgen-gallery/