Images not showing on the Slider

Hi,

I recently downloaded the pinboard theme and was trying to set up the slider for my blogpost. I added the featured images to my posts and marked them as ‘Sticky’. I see the slider showing up on my site and the images don’t load up. What could be the reason?.

Do I need to have the images on a particular size for it to show up on slider. Any help on this is appreciated.

Thanks !