Bootstrap form center alignment issue: how can I align vertically and horizontally?

Question

I am trying to vertically and horizontally align my form into the centre of my screen but it does not do it could someone please help me resolve this error

<div class="container">
<div class="row vh-100">
<div class="d-flex align-items-center">
    <form class="form" action="" method="post">
        <h1 class="login-title">Registration</h1>
        <input type="text" class="login-input" name="username" placeholder="Username" required />
        <input type="text" class="login-input" name="email" placeholder="Email Adress">
        <input type="password" class="login-input" name="password" placeholder="Password">
        <input type="submit" name="submit" value="Register" class="login-button">
        <p class="link"><a href="login.php">Click to Login</a></p>
    </form>
    </div>
    </div>
    </div>

Alignment to the centre of the screen