Remove the quote around Rubik, that should do the trick.
font-family: Rubik, sans-serif;
Also, add this block in native libraries instead of HTML. anything you add in native libraries gets injected inside head tag.
<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=Rubik:ital,wght@0,300..900;1,300..900&display=swap" rel="stylesheet">
Let me know if that helped!