It's important to crop or scale images for featured content sliders to be exactly the same width and height. You may lose action text on some of them if they are not all the same size. 

If the action text doesn't display on any of your featured content sliders, you're probably using the Victory theme. The Victory theme is built to not show action text with featured content slider images.  

I'd recommend using the Aware theme as it is built with responsive design - so visitors will have a good navigation experience whether on a tablet, mobile phone or computer. Information on making the most of the themes is available in our stock theme guidelines.