Meu incone não aparece | CSS: dispondo elementos com Flexbox e Grid

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>HZC | Home</title>
    <link rel="preconnect" href="https://fonts.googleapis.com">
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
    <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Open+Sans:wght@400;600;700&display=swap">
    <link rel="stylesheet" href="./css/reset.css">
    <link rel="stylesheet" href="./css/estilo.css">

</head>
<body>
    <header class="cabecalho">
        <button class="cabecalho__menu"><i></i></button>
        <img src="img/logo.svg" alt="logotipo da HZC" class="cabecalho__logo">
        <button class="cabecalho__notificacao"> <i></i>     </button>
    </header>

</body>
</html>

@font-face {
    font-family: 'icones';
    src: url("./font/icones.ttf");
}
body {
    background-color: #1D232A;
    font-family: 'Open Sans','icones';
    color: #FFFFFF;
}

.cabecalho {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: #15191C
    padding:8px 16px;
    box-shadow: 0px 4px 4px rgba(0, 0, 0, 0.16);
}

cabecalho__menu i::after {
    content: "\e904";
}

cabecalho__notificacao i::before {
    content: "\e906"

Meus incones não aparecem....

.cabecalho__menu i::before { content:"\e904"; font-family: "icones"; font-size: 27px; } .cabecalho__notificacao i::before { content: "\e906"; font-family: "icones"; font-size: 27px; }