Show hidden div, auto-hide the others.

Dear coders,

I can’t seem to make this work on my wordpress installation https://www.aspar.cz

This is the script: https://jsfiddle.net/YsmVn/63/

I added the javascript to my header.php file (https://test.mediawebs.eu/showhide.js) and the html code to the following page: https://aspar.cz/instalace/. The javascript doesn’t seem to kick in and I have no idea why.

I can give you access to the wordpress installation if needed.

George