Images on home page

Hi everyone

I can’t find the following in the forums and I’m hoping someone can help me.

I’m using the directory theme with no child theme. When I go into categories and add icon it puts the icon next to the category in the search page which is fine. However the images next to the categories on my home page are blank grey boxes. Apart from three of them which actually have the text of the category in the grey box for some reason.

Can someone tell me how to change these please. (I haven’t changed any setting s on the homepage they are all as I downloaded the theme).

Many thanks
Lee