In the siteassistpro_css/content.css file, remove the overlow: auto property from the "html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6" selector, this is causing the problem:
html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6 {
margin: 0;
padding: 0;
border: 0;
outline: 0;
font-size: 100%;
/*overflow:auto;*/
}