Thank you very much!
It was a Problem with the “Widget CSS Classes” Plugin. Your Tipp with the ID was the solution.
I have the same Problem. The sidebar widget does not work anymore since an update to version 2.3.1 and it does not work with the current(2.4) version.
I get the following error message
Error: TypeError: d is undefined
… frontend.min.js?ver=2.4 Line: 2
This is the Website
http://kiddyspace.com/kiddyspaces/