<strong> Tag does not work! within <li> list item tag

I would like to use some of the <.strong> and <.em> tags within <.li> nested in <.ul>. The <.em> works and it gaves me the text as bold. However, the <.strong> tag does not show the text as italic.

<em> renders as italic; <strong> renders as bold.

What we don’t see is how these two are aurally rendered.

<em> renders visually the same as <i>, and <strong> renders visually the same as <b>. However, when the user agent is a screen reader, there is a change of voice with both semantic elements, (EM, STRONG) and no change of voice with the strictly visual elements.

Please show us your markup and screenshot of the rendering so we may confirm your observations.