its just not working?

installed and activated the plugin, but when i click on an image (which i included in a page) like

<a href="thelink"><img src="thesource" alt="thetext" class="alignnone size-medium wp-image-1050" /></a>

it just loads the link without showing the lightbox?

https://www.ads-software.com/plugins/iw-magnific-popup/