Thanks for sharing your credentials. I went ahead and checked your website dashboard, it seems that you have not set a featured image in the portfolio items (Portfolio Posts). I have set featured image in the Portfolio Posts. In the Essential Grid setting, you did not set any image source(Media source) to display.
You need to set Item Media Source Order as Featured Image to display Portfolio Post Image.
Please have a look at the screenshot given below for Essential Grid settings
Output after featured image set
Please set features image of Portfolio items as per your design.