I am not sure about this, but would you please kindly do a test for us? Would you please kindly dd a test page and then add a classic section to it? To add a classic section instead of the normal section you will need to hold the CMD key on Mac or CTRL key on Windows and the Section add option turns in to Classic Section:
Then please add the Essential Grid there and see if it shows the icons.
Another point is that in the screenshot it shows the icons as squares, that shows either you did not set the font of the icon to be font awesome for example or you have a problem rendering the font icons on your server which can be solved by following the steps below:
I checked the given page but I could not see the icons to be able to follow up. If the suggestions above do not fix the issue, kindly get back to us with the step by step process of adding the icon to be able to follow up and see where is the issue.