I am trying to ad video to a slider. I have tried the “add video” option on multiple sliders included in the Pro version (including the ‘video slider’). I enter the URL of the video (YouTube) – but when I ‘preview’ the slider, nothing is showing up – it’s just a blank white slider. Is there a step I am missing? I have tried multiple video (YouTube) URLs, on different sliders, so I am not sure the step that I’m missing here.