>Upload Images> does not work. In any Section

Hey Zerif Lite team,

thx for this quick and easy and well designed template.
I have one – big – problem:
I want to upload images in Sections ( team, focus, testimonials, clients )
>> but it does not work. Hitting the Upload Images has no effect.
Nothing happens at all.
I even tried to drag and drop an image onto the field. What happens is: the path on my computer towards that pic is written. But again – when hitting the upload button – there′s no effect.
At the moment I can not add any picture – nor by uploading or by taking from the WP-mediathek.
The only image that has worked so far is the background picture.

I really do appreciate your help, to be able to go on with my work.
Best wishes from Berlin,
Kassandra