Post Image Thumbnail Does not display After making a post


I came across CALI THEME while searching for a theme for my slide website and i used it to set up the set site but when i make any post, the images in the post does not show (display) the post image thumbnail both and also on the latest post widget as it displays on the CALI THEME DEMO SITE. Please is their any fix for this? here is the site

Hello there,

Thank you for using Cali. Please share share a link to one of your post that should be displaying the thumbnail image. Does this issue happen on all posts? Or just particular ones?