Question about my header display when sharing my site on FB

Shared my site with a few friends for feedback and am enclosing a screenshot of how that showed up on the group page. Also, no photo showed up. When I shared it with a friend in a private message five minutes later, the photo showed up, but it still has the old tagline. Why does it show up differently each time I share it and is there a way to have it show up consistently as it is now? Thanks for your help!!!