Woocommerce Version 3.3.1 - Released 2018-02-06  is not compatible with Salient Theme Version 8.5.3  . 

Kindly do not Update Woocommerce and Downgrade if you have done so until a Salient Theme Update is released .

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Make button open lightbox

The correct HTML to add a button with an icon that links to a video would be:

 
<a class="nectar_video_lightbox nectar-button small accent-color regular-button" target="_blank" href="https://www.youtube.com/watch?v=yarB1NCyqfs" data-color-override="false" data-hover-color-override="false" data-hover-text-color-override="#fff" style="visibility: visible;" rel="prettyPhoto"><span>Test Span</span> </a>

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