Fixed, it was the classic directory issue.
Foundation stores Zepto, JQuery and foundation.min.js in js/vendor/
I have them in my install unter assets/js/vendor
Also my CMS wants a leading slash, so I need /assets/js/vendor
. The JQuery-path had no assets/ and for all 3 scripts the slash in front of assests was missing. After I changed that, the menu works.
I use the firebug console to debug. The error
ReferenceError: $ is not defined
put me on the right path. If
<script>
$(document).foundation();
</script>
has issues, than something must be wrong here
<script>
document.write('<script src=' +
('__proto__' in {} ? '/assets/js/vendor/zepto' : '/assets/js/vendor/jquery') +
'.js><\/script>')
</script>
<script src="/assets/js/foundation.min.js"></script>
Those three Scripts are the foundation of Foundation. If one can´t be loaded, Foundation will not work properly