Please also note that following change also needs to be 
made for the module to function correctly. 

--[EDIT]-----------------------------------------------------

/inc/design.inc.php

--[FIND]-----------------------------------------------------

function PageCode($oTemplate = null) {
    global $echo;
	global $_page;
	global $_page_cont;	
	global $oSysTemplate;

--[ADD AFTER]-----------------------------------------------
				
//[START DeeEmm Maintenance Mode MOD]
$sPageUrl = 'http://' . $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];

if (getParam('dm_maint_enabled') == 'on' && $site['url_admin'] !== $sPageUrl) {
	if (!$GLOBALS['logged']['admin']) {
		echo getParam('dm_maint_page_html');
		exit;
	}
}
//[END DeeEmm Maintenance Mode MOD]