Error 500 Edit Template / Header

[fmslick]

Hello.

I am getting an error when I go to edit the header of my Template. This is new install with no mods or plugins but what comes with MyBB, the style is Revo1817 or revolution Gaming. I have tested to see if I can edit other Template / header like the one MyBB comes with and I can, its just like the Revo1817 one will not let me  ....

Revo1817/revolution Gaming: #8_stable https://community.mybb.com/mods.php?action=view&pid=196

Installed everything via FTP and using cpanel to make the database/username then ran the installer via webui. I am not getting any errors in log files.

Server:
PHP v7.4
litespeed web server
MariaDB

----
Header Template:

<a name="top" id="top"></a> <br /> <br />
<div id="mainwidth"> 

<div id="container">
<div id="content">
	
<div class="menu">
<ul>
<li id="nav-portal"><a href="{$mybb->settings['bburl']}/portal.php"><i style="font-size: 12px;" class="fa fa-home fa-fw"></i> Home</a></li>
<li id="nav-forums"> <a href="{$mybb->settings['bburl']}/index.php"><i style="font-size: 12px;" class="fa fa-comments fa-fw"></i> Forums</a></li>
<li id="nav-search"> <a href="{$mybb->settings['bburl']}/search.php"><i style="font-size: 12px;" class="fa fa-search fa-fw"></i>  {$lang->toplinks_search}</a></li>
<li id="nav-member"> <a href="{$mybb->settings['bburl']}/memberlist.php"><i style="font-size: 12px;" class="fa fa-users fa-fw"></i> Members</a></li>
<li id="nav-calendar"> <a href="{$mybb->settings['bburl']}/calendar.php"><i style="font-size: 12px;" class="fa fa-calendar fa-fw"></i> {$lang->toplinks_calendar}</a></li>
<li id="nav-help"> <a href="{$mybb->settings['bburl']}/misc.php?action=help"><i style="font-size: 12px;" class="fa fa-info fa-fw"></i> {$lang->toplinks_help}</a></li>
  <li><a href='javascript:;' id="extraslink"><i style="font-size: 14px;" class="fa fa-angle-down fa-fw"></i>Extras</a></li>
	     <ul>
            </div> 
  <div id="extraslink_popup" class="popup_menu" style="display: none;">
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/stats.php" class="popup_item">Forum stats</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/showteam.php" class="popup_item">Show team</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/search.php?action=getnew" class="popup_item">{$lang->welcome_newposts}</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/search.php?action=getdaily" class="popup_item">{$lang->welcome_todaysposts}</a>
      </div>
      <div class="popup_item_container">
        <a href="*" class="popup_item">Link five here</a>
      </div>
  </div>
	
<div class="topbar"> 
<table width="100%" cellspacing="0" cellpadding="{$theme['tablespace']}" border="0">
<tr>
<td valign="top">
	
<div id="logo" class="float_left">
	<a href="{$mybb->settings['bburl']}/index.php"><img src="{$theme['logo']}" alt="{$mybb->settings['bbname']}" /></a>
	</div>	
	
</td>
<td>&nbsp;</td>
<td valign="bottom">
	
<div style="margin-top: 120px;"><div class="userbg">{$welcomeblock}</div></div>
	
</td>
</tr>
</table>	
</div>
	
         <br />
	
			<div class="wrapper">
				{$pm_notice}
				{$bannedwarning}
				{$bbclosedwarning}
				{$unreadreports}
				{$pending_joinrequests}
				{$awaitingusers}
				<navigation>
				<br />
					
					
<script type="text/javascript">
// <!--
    if(use_xmlhttprequest == "1")
    {
        $("#extraslink").popupMenu();
    }
// -->
</script>

Thanks.

---

UPDATE:

As I was doing some testing and removed some code I found out this javascript "<a href='javascript:;' id="extraslink">" is making some type of issue! So I removed it and now I can save with out getting an error 500...

  <li><a href='javascript:;' id="extraslink"><i style="font-size: 14px;" class="fa fa-angle-down fa-fw"></i>Extras</a></li>
	     <ul>

            </div> (HAD TO PUT THIS END TAG BACK)

  <div id="extraslink_popup" class="popup_menu" style="display: none;">
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/stats.php" class="popup_item">Forum stats</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/showteam.php" class="popup_item">Show team</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/search.php?action=getnew" class="popup_item">{$lang->welcome_newposts}</a>
      </div>
      <div class="popup_item_container">
        <a href="{$mybb->settings['bburl']}/search.php?action=getdaily" class="popup_item">{$lang->welcome_todaysposts}</a>
      </div>
      <div class="popup_item_container">
        <a href="*" class="popup_item">Link five here</a>
      </div>
  </div>

[.m.]

have you checked server error log ? recent entries might refer to mod_security ...

[fmslick]

have you checked server error log ? recent entries might refer to mod_security ...

I didn't see anything in the error logs but I will have another look, and a look into the mod security! 

Thanks @.m.

EDIT: Yes mod_security was the issue more so the js code. after adding the solution to my .htaccess I can now put back the original template script.