Are you talking about Illustrator .eps files?
First, that’s an archaic file format and is generally avoided these days because it does not support transparency (and does all kinds of horrible things to files that do have transparency.)
It is an encapsulated Postscript file. Neither Mac nor Windows are set up to read Postscript for thumbnails any more. I see .eps files as icons too and I’m on a mac. You need a viewer that can read them. I’ve seen a few mentioned online, but not for .eps.
I don’t have a recommendation. I don’t see .eps files enough these days to warrant the hassle.
Can you see thumbs of the other Adobe file types? That used to be a problem on Windows machines as well.