Try being explicit about all the border properties. For example:
border:1px solid black;
See Border shorthand property. Although the other bits are optional some browsers don’t set the width or colour to a default you’d expect. In your case I’d bet that it’s the width that’s zero unless specified.
can use
border-width:2px;
border-style:solid;
border-color:black;
or as shorthand
border: 2px solid black