The preview or build mode does not support playing of video, which is why we show a preview image.

Sometimes, even when the format is supported, the video host does not provide a preview image we can display. 

When that happens you will see a grey box with a play button.  This is only displayed when building.  

This is how video shows when there is not a preview image supplied. 

If you would like to see the video, within your StickyAlbum or StickyFolios publish your Folio then open the link to in a new browser window.