In the testimonials-widget.php (located in the plugins->testimonials-widget directory ) Find the following line of code
<script type="text/javascript">
function nextTestimonial$widget_number() {
if (!jQuery('.$id_base').first().hasClass('hovered'))
you want to change the .first() method to .eq(0)
<script type="text/javascript">
function nextTestimonial$widget_number() {
if (!jQuery('.$id_base').eq(0).hasClass('hovered'))
It works on some themes, and some it does not as I have one clients website that works with .first() and others that need the .eq(0) . Also make sure you have loaded JQuery in your header correctly.