Read the markup
Open the file and find the <form> tag. If it has no action, or the action is #, the browser has nowhere to send anything.
<!-- Goes nowhere: no action attribute -->
<form>
<input type="email" name="email">
<button>Notify me</button>
</form>
<!-- Goes somewhere: an endpoint that is yours -->
<form action="https://your-endpoint" method="POST">
<input type="email" name="email" required>
<button>Notify me</button>
</form>