Hi, there are many things going wrong on your site so it’s hard to tell which one is directly responsible for FancyBox not working. To name a few:
1. Your theme seems to be missing the obligatory wp_footer() call. Or more likely the while footer.php template file. The html and body tags (and probably others) are not closed and there are no scripts in the footer.
2. There are four different versions of the jQuery library included.
...
<script type='text/javascript' src='https://www.seilpark-engadin.ch/wp-includes/js/jquery/jquery.js?ver=1.11.2'></script>
...
<!-------Enabling Scripts-------->
<script src="https://code.jquery.com/jquery-latest.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js?ver=3.0.1"></script>
There can be only one jQuery. Moreover, the last one (that will overwrite all previous ones) is incompatible with Easy FancyBox. You’ll need to find out where these last three insertions are coming from. The theme itself or another plugin?
3. There is a blocking error coming from the themes menu-functions.js script:
Uncaught TypeError: jQuery(...).on is not a function
This is caused by that old jQuery library inclusion mentioned above.
4. FancyBox script itself is included twice. NextGEN is loading its own FancyBox script alongside Easy FancyBox’s one. You’ll need to choose between them. Either remove the Easy FancyBox plugin or find the option in NextGEN to disable the lightbox script inclusion.
After you’ve solved these issues, you might be closer to a working lightbox ??
