Creio q o problema não seja esse pois todo o restante do CSS está funcionando perfeitamente, inclusive o mesmo cabeçalho em outras páginas do site está funcionando.
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Home - Cuide de você!</title>
<script src="home.js"></script>
<link rel="icon" type="image/png" href="imagens/favicon.png" />
<link rel="stylesheet" href="./style.css" />
<link rel="preconnect" href="https://fonts.googleapis.com" />
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
<link href="https://fonts.googleapis.com/css2?family=Mukta:wght@800&display=swap" rel="stylesheet"/>
<link rel="preconnect" href="https://fonts.googleapis.com" />
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
<link
href="https://fonts.googleapis.com/css2?family=Mukta:wght@600&display=swap"
rel="stylesheet"
/>
</head>
<body>
<header>
<nav class="nav-bar">
<div class="logotipo">
<a class="logo" href="index.html" title="Renato Veronezi">
<img
src="imagens/logo.png"
alt="Logomarca"
height="40px"
width="200px"
/>
</a>
</div>
<div class="nav-list">
<ul>
<li class="nav-item">
<a class="nav-link" href="index.html">Home</a>
</li>
<li class="nav-item">
<a class="nav-link" href="about.html">Sobre</a>
</li>
<li class="nav-item">
<a class="nav-link" href="contact.html">Contato</a>
</li>
</ul>
<button id="button-button">
<a class="button" href="schedule.html">Agendamento</a>
</button>
</div>
<div class="mobile-menu-icon">
<button>
<img class="icon" src="/imagens/menu-svgrepo-com.svg" />
</button>
</div>
</nav>
<div class="mobile-menu">
<ul>
<li class="nav-item">
<a class="nav-link" href="index.html">Home</a>
</li>
<li class="nav-item">
<a class="nav-link" href="about.html">Sobre</a>
</li>
<li class="nav-item">
<a class="nav-link" href="contact.html">Contato</a>
</li>
</ul>
<button id="button-button">
<a class="button" href="schedule.html">Agendamento</a>
</button>
</div>
</header>