Move the line <body class="cover"> to where you have <body> and delete the line <body>, which is a duplicate <body> and overrides the first <body class="cover"> line.
Here is the revised code:
<?xml version='1.0' encoding='utf-8'?>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<title>Unknown</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<link href="stylesheet.css" rel="stylesheet" type="text/css"/>
<link href="page_styles.css" rel="stylesheet" type="text/css"/>
<style type="text/css">
@page {
margin-bottom: 0pt;
margin-left: 0px;
margin-right: 0px;
margin-top: 0pt;
padding: 0px
}
</style>
</head>
<body class="cover">
<p class="image1">
<img src="images/CC3.jpeg" alt="Image" class="image" />
</p>
</body></html>