CUNY Academic Commons

The Bravada theme has a bit of CSS that does the following:

.bravada-stripped-table .main td {
    border-top: 1px solid transparent;
}

So it seems to be an intentional design decision by the theme author.

If you want override, the following custom CSS will probably work:

.bravada-stripped-table .main td {
    border-top: 1px solid #000;
}