No Popup Window After Clicking the Share Buttons

If you are clicking on one of the share buttons and nothing happens check first if the mashshare javascript file mashsb.min.js is loaded. If this is not the case its possible that your theme is not using the WordPress Hook wp_head() for embedding plugin scripts.

So if you have no chance to update or change your theme do some hard-coding and put the following line into the head template of your theme file;

<script type='text/javascript' src='http://yourwebsite.com/wp-content/plugins/mashsharer/assets/mashsharer.js?ver=1.1'></script>

Easier and more recommend is to embed the wp_head() function into the header.php template file. Please ask the developer of your theme to do so because this is good WordPress practice.