in the webassist/themes/<your theme>/plugins/plugin.php file (where <your theme> is the theme you are using), change:
$WASideMenu = new
WA_Include('../../../plugins/side_menu/nested_accordion/sidemenu.php');
to either:
$WASideMenu = new WA_Include('../../../plugins/side_menu/sidemenu.php');
or:
$WASideMenu = new WA_Include('../../../plugins/side_menu/accordion/sidemenu.php');