Switching the uploader does not work

I have a problem with the switching of the uploader, this problem is in photo, files, sounds, and videos. 

It can be simply not switching, it always appears just this Loading icon. 

If I but the uploader in the admin adjusting individually he funkioniert, just hold the switch on the website does not work. 

Hat an idea where I can one look for the error?

A guess is that there is a javascript.jquery conflict.  This can be caused by a template that was added to the site that includes javascript/jquery codes (and I am against templates that do more than HTML and CSS changes for this reason).  If you are using a third party template, switch the site to the UNI template for testing.  You may still see the problem if code was added to the base template headers.

Sometimes it could be an issue of wrong js files permissions. Check your browser console for js errors or post here your site URL and we'll check it.

As well as the above, if you have one of those "spaces in username" mods installed, they will break the JavaScript in some cases where the username has a space in it, or any other non-standard character.