The head is too big for WhatsApp to read

WhatsApp reads only the start of a page when it makes a link preview, and says so: the <head> section "must appear within the first 300KB of the HTML". When a page inlines its stylesheets, fonts or a large block of script data into the head, </head> lands past that point, WhatsApp never reaches your sharing tags, and a link pasted into a chat shows as a bare address, while every other network previews it perfectly.

Source: WhatsApp link previews.

Put the sharing tags first, straight after <meta charset> and <title>, and move what is heavy out of the head: link stylesheets instead of inlining them, load fonts from files rather than as base64, and move large JSON blobs (__NEXT_DATA__, a page builder's state) to the end of <body>.

<head>
  <meta charset="utf-8" />
  <title>…</title>
  <meta property="og:title" content="…" />
  <meta property="og:image" content="https://www.example.com/share.png" />
  <!-- then everything else -->
</head>