vb net Click a tabbutton on a webpage

Completely new to this, I am unable to get my code to click and activate a tabbutton on a webpage, the part of the website I am trying to activate is

class="tabButton EngagementsHistoryTable"

"Web History"

<ul class="tabs_manager_buttons_container lpview_tabs_manager_buttons_container">
   <li class="lpview_underLine underLine" style="left: 0px; width: 132px; 
   display: block;"></li>
 <li class="tabButton VisitorListTable first active">
    <span class="lpview_tabButton tabButtonText" title="Web Visitors" 
     tooltip-align="left" tooltip-delay="1500" tooltip-text="Web Visitors">Web 
     Visitors</span></li>
 <li class="tabButton EngagementsHistoryTable">
    <span class="lpview_tabButton tabButtonText" title="Web History" tooltip- 
     align="left" tooltip-delay="1500" tooltip-text="Web History">Web 
     History</span> 
 </li>
<li class="tabButton AgentListTable"><span class="lpview_tabButton 
     tabButtonText" title="Agents" tooltip-align="left" tooltip-delay="1500" 
     tooltip-text="Agents">Agents</span></li>
</ul>

The below code executes the click but nothing happens.

 For Each element As HtmlElement In WebBrowser1.Document.GetElementsByTagName("li")
    If element.GetAttribute("className") = "tabButton EngagementsHistoryTable" Then
           element.InvokeMember("click")
    End If
 Next